How do multiple screens work?

If you are going to work with different real screens, you can pass directly data from one screen to other, using the block "open another screen with value" or you can store it in tinyDB to be available in other screens.

You can also work with Vertical Arrangement (hiding/showing them) to simulate different screens (also called virtual screens):

In this case you don't need to store/pass the data because you are always in the same screen.