What is a scope ?

scope is an area meaning some range in code where each name is valid.

Maybe you need some specific description to your issue. Please show enough code which represents what would be your issue.

Take this example

Code Block 
class MyClass {
  var classScopeVar = 1   // This is visible in the scope of the class
  func someFunc() {
    var funcScopeVar = 2   // This is only defined (hence visible) in the scope of the func
    print("classScopeVar", classScopeVar)
    print("funcScopeVar", funcScopeVar)
  }
  func otherFunc() {
    print("classScopeVar", classScopeVar)  // This is visible in the scope of the class, hence it works
    print("funcScopeVar", funcScopeVar)  // This is visible only in the scope of someFunc, hence compiler error here
  }
}

So, in your case, check where you declared the button.
If it is inside a func, it will not be visible outside of the func.
You need to declare it at the class level most likely.
If you have created a button in storyboard, you need to connect to an IBOutlet to reference it (control-drag from the button in storyboard to some place in the class ; the following will be automatically created once you give signIn as the name for the button):

Code Block 
@IBOutlet weak var signIn: UIButton!

Scope is also important because local declaration is considered in priority.

If you write

Code Block 
  func yetAnotherFunc() {
    var classScopeVar = 3 // You redeclare a new var with the same name
    print("classScopeVar", classScopeVar)  // You will get 3, not 1
   // If you want to access the initial var
    print("real classScopeVar", self.classScopeVar)  // You will get  1
  }

I have just finish reading your examples and I know that they are right.
I want to add a Button in my tutorial with a screen touch to see if the mobile device recognizes the touch for the button and receive a scope 'declare' error from the complier.

Do you have time to give me a example of a button with a declared scope ?

Kind Regards

In the previous example, let's create a signIn button in storyboard, in the viewController.

• Connect (control drag) this button to the class code, just below the class declaration. Give the name signIn.

• You need also to create an action : control-drag again from the button in storyboard, to the code, and select Action. Give it a name like pressSignIn

The button has not a 'declared' scope, it has a scope depending how it is declared.
Type the new instructions as shown below
You should get something like:

Code Block 
class MyClass {
    @IBOutlet weak var signIn: UIButton!   // see the black dot at the left
    var classScopeVar = 1   // This is visible in the scope of the class
    @IBAction func pressSignIn(_ sender: UIButton) {  // button is in fact signIn
          print("Button pressed")
          print("It is signIn, which is visible in scope", signIn.titleLabel?.text ?? "")  // We check the button is visible here
          // You could also have written:
          print("Sender", sender.titleLabel?.text ?? "")    // The same result
    }
  func someFunc() {
    var funcScopeVar = 2   // This is only defined (hence visible) in the scope of the func
    print("classScopeVar", classScopeVar)
    print("funcScopeVar", funcScopeVar)
    print("I can also call from this func", signIn.titleLabel?.text ?? "")  // We check the button is visible here
   // But the following would fail:
   print("Sender", sender.titleLabel?.text ?? "")    // sender is not visible here, only in the IBAction func. So that will cause a compiler error. Comment out this line to be able to compile and run.
  }
  func otherFunc() {
    print("classScopeVar", classScopeVar)  // This is visible in the scope of the class, hence it works
    print("funcScopeVar", funcScopeVar)  // This is visible only in the scope of someFunc, hence compiler error here
  }
}

If that's OK, don't forget to close the thread on this answer.
Otherwise, please explain what is still unclear for you.

I will learn to code it myself and if I will obtain a negative result, I will learn with your example.

Kind Regards

Code Block 
//
//  BadgeBackground.swift
//  Landmarks
//
//  Created by Besleaga Alexandru Marian on 5/11/21.
//
import SwiftUI
struct BadgeBackground: View {
    var body: some View {
        Path { path in
            var width: CGFloat = 100.0
                        let height = width
                        path.move(
                            to: CGPoint(
                                x: width * 0.95,
                                y: height * 0.20
                            )
                        )
            
            HexagonParameters.segments.forEach { segment in
                            path.addLine(
                                to: CGPoint(
                                    x: width * segment.line.x,
                                    y: height * segment.line.y
                                )
                            )
                        }
            
                }
                .fill(Color.black)
    }
}
struct BadgeBackground_Previews: PreviewProvider {
    static var previews: some View {
        BadgeBackground()
    }
}
And I receive the following error "Cannot find 'HexagonParameters' in scope"
How do I code the the scope for HexagonParameters ?

And I receive the following error "Cannot find 'HexagonParameters' in scope"

How do I code the the scope for HexagonParameters ?

I guess you took the code from a tutorial of SwiftUI and HexagonParameters is a name of a struct.
In this case, scope is somewhere in your project.
You create a new file named HexagonParameters.swift in your project and put the definition of it into the file.
https://developer.apple.com/tutorials/swiftui/drawing-paths-and-shapes

Do you understand the problem ?
You use HexagonParameters, but is is nowhere defined. How could the compiler guess what it is ?

In your code, just add the struct definition:

Code Block 
import SwiftUI
struct HexagonParameters {
    struct Segment {
        let useWidth: (CGFloat, CGFloat, CGFloat)
        let xFactors: (CGFloat, CGFloat, CGFloat)
        let useHeight: (CGFloat, CGFloat, CGFloat)
        let yFactors: (CGFloat, CGFloat, CGFloat)
    }
    
    static let adjustment: CGFloat = 0.085
    static let points = [
        Segment(
            useWidth:  (1.00, 1.00, 1.00),
            xFactors:  (0.60, 0.40, 0.50),
            useHeight: (1.00, 1.00, 0.00),
            yFactors:  (0.05, 0.05, 0.00)
        ),
        Segment(
            useWidth:  (1.00, 1.00, 0.00),
            xFactors:  (0.05, 0.00, 0.00),
            useHeight: (1.00, 1.00, 1.00),
            yFactors:  (0.20 + adjustment, 0.30 + adjustment, 0.25 + adjustment)
        ),
        Segment(
            useWidth:  (1.00, 1.00, 0.00),
            xFactors:  (0.00, 0.05, 0.00),
            useHeight: (1.00, 1.00, 1.00),
            yFactors:  (0.70 - adjustment, 0.80 - adjustment, 0.75 - adjustment)
        ),
        Segment(
            useWidth:  (1.00, 1.00, 1.00),
            xFactors:  (0.40, 0.60, 0.50),
            useHeight: (1.00, 1.00, 1.00),
            yFactors:  (0.95, 0.95, 1.00)
        ),
        Segment(
            useWidth:  (1.00, 1.00, 1.00),
            xFactors:  (0.95, 1.00, 1.00),
            useHeight: (1.00, 1.00, 1.00),
            yFactors:  (0.80 - adjustment, 0.70 - adjustment, 0.75 - adjustment)
        ),
        Segment(
            useWidth:  (1.00, 1.00, 1.00),
            xFactors:  (1.00, 0.95, 1.00),
            useHeight: (1.00, 1.00, 1.00),
            yFactors:  (0.30 + adjustment, 0.20 + adjustment, 0.25 + adjustment)
        )
    ]
}
struct BadgeBackground: View {
    var body: some View {
        Path { path in
                var width: CGFloat = 100.0
                        let height = width
                        path.move(
                            to: CGPoint(
                                x: width * 0.95,
                                y: height * 0.20
                            )
                        )
             HexagonParameters.segments.forEach { segment in
                            path.addLine(
                                to: CGPoint(
                                    x: width * segment.line.x,
                                    y: height * segment.line.y
                                )
                            )
                        }
                }
                .fill(Color.black)
    }
}
struct BadgeBackground_Previews: PreviewProvider {
    static var previews: some View {
        BadgeBackground()
    }
}

HexagonParamaters.swift

Code Block 
//
//  HexagonParameters.swift
//  Landmarks
//
//  Created by Besleaga Alexandru Marian on 5/11/21.
//
import Foundation
import CoreGraphics
struct HexagonParamaters{
    struct Segment {
            let line: CGPoint
            let curve: CGPoint
            let control: CGPoint
        }
    
    static let adjustment: CGFloat = 0.085
    
    static let segments = [
        Segment(
                    line:    CGPoint(x: 0.60, y: 0.05),
                    curve:   CGPoint(x: 0.40, y: 0.05),
                    control: CGPoint(x: 0.50, y: 0.00)
                ),
                Segment(
                    line:    CGPoint(x: 0.05, y: 0.20),
                    curve:   CGPoint(x: 0.00, y: 0.30),
                    control: CGPoint(x: 0.00, y: 0.25)
                ),
                Segment(
                    line:    CGPoint(x: 0.00, y: 0.70),
                    curve:   CGPoint(x: 0.05, y: 0.80),
                    control: CGPoint(x: 0.00, y: 0.75)
                ),
                Segment(
                    line:    CGPoint(x: 0.40, y: 0.95),
                    curve:   CGPoint(x: 0.60, y: 0.95),
                    control: CGPoint(x: 0.50, y: 1.00)
                ),
                Segment(
                    line:    CGPoint(x: 0.95, y: 0.80),
                    curve:   CGPoint(x: 1.00, y: 0.70),
                    control: CGPoint(x: 1.00, y: 0.75)
                ),
                Segment(
                    line:    CGPoint(x: 1.00, y: 0.30),
                    curve:   CGPoint(x: 0.95, y: 0.20),
                    control: CGPoint(x: 1.00, y: 0.25)
                )
        ]
}

BadgeBackground.swift

Code Block 
//
//  BadgeBackground.swift
//  Landmarks
//
//  Created by Besleaga Alexandru Marian on 5/11/21.
//
import SwiftUI
struct BadgeBackground: View {
    var body: some View {
        Path { path in
            var width: CGFloat = 100.0
                        let height = width
                        path.move(
                            to: CGPoint(
                                x: width * 0.95,
                                y: height * (0.20 + HexagonParameters.adjustment)
                            )
                        )
            
            HexagonParameters.segments.forEach { segment in
                            path.addLine(
                                to: CGPoint(
                                    x: width * segment.line.x,
                                    y: height * segment.line.y
                                )
                            )
                
                path.addQuadCurve(
                                    to: CGPoint(
                                        x: width * segment.curve.x,
                                        y: height * segment.curve.y
                                    ),
                                    control: CGPoint(
                                        x: width * segment.control.x,
                                        y: height * segment.control.y
                                    )
                                )
                        }
            
                }
                .fill(Color.black)
    }
}
struct BadgeBackground_Previews: PreviewProvider {
    static var previews: some View {
        BadgeBackground()
    }
}

Code Block 
Cannot find 'HexagonParameters' in scope

What should I do ?

You have a file HexagonParameters.swift, but the name of the struct in it is being HexagonParamaters, not HexagonParameters.

Wrong:

Code Block 
struct HexagonParamaters{

Right:

Code Block 
struct HexagonParameters{