Thank you for the reply. I guess I have been working with this NASA site and it has become second nature to just say NASA API.
This is the URL
https://api.nasa.gov/
in particular:
Mars Rover Photos - There are multiple URLs attached to this sub site. Per site description:
"This API is designed to collect image data gathered by NASA's Curiosity, Opportunity, and Spirit rovers on Mars and make it more easily available to other developers, educators, and citizen scientists. This API is maintained by Chris Cerami.
Each rover has its own set of photos stored in the database, which can be queried separately. There are several possible queries that can be made against the API. Photos are organized by the sol (Martian rotation or day) on which they were taken, counting up from the rover's landing date. A photo taken on Curiosity's 1000th Martian sol exploring Mars, for example, will have a sol attribute of 1000. If instead you prefer to search by the Earth date on which a photo was taken, you can do that, too.
https://api.nasa.gov/mars-photos/api/v1/rovers/curiosity/photos?sol=1000&api_key=DEMO_KEY:
https://api.nasa.gov/mars-photos/api/v1/rovers/curiosity/photos?sol=1000&camera=fhaz&api_key=DEMO_KEY
https://api.nasa.gov/mars-photos/api/v1/rovers/curiosity/photos?sol=1000&page=2&api_key=DEMO_KEY
As to what I am attempting: to build an app that will download some of the Photos from the various rovers that are on Mars and their different cameras.
I have done a similar app with the APOD site (on the same NASA API / URL location which displays the "Photo of the Day" and a brief description of the photo.
Hopefully, this provide some of the information I left out in my first post - what the Site, URL, and what I am attempting.