How do I adjust the layout of a view according to the size of the view?

I can't remember what that is called that we use to adjust the layout of a view according to the size of the view. It takes account the device and whether it is in the right hand pane on an iPad. I need to know what that is called so I can look it up to study how to do it. I don't necessarily need to use interface builder. I want to use whatever is the most effective way.