What are the other "home" screens called?
From source code of Launcher3 in Android 6.0.1 r16: 


  The workspace is a wide area with a wallpaper and a finite number of pages. Each page contains a number of icons, folders or widgets the user can interact with.


Honestly, this is the first time I heard the term workspace in context of a launcher for Android, but if you want a standard term, there you have it.

The page with home icon is referred as default page and the page currently displayed to the user is called current page. This is what I understood from this line in the source code of the said launcher.

Edit: After checking the sample of Home app in Android 6.0.1 r16 (they are using a very old sample for developers), I noticed this line inter alia and I conclude that each page can be referred to as home screen and you can reference another page by calling it previous, succeeding, or preceding home screen or by using the numbers available through scroll, such as home screen 3.