I have one, too! It's easy to understand:
Some games you have to have cards in order to play; EX Mario Kart 8, Lugi's manision, ect.
So the other ones, you will need to save progress on. Examples like Zelda, you need to save your progress before going into a new game.
You can take screenshots by using the little square button on the bottom left corner JoyCon.
If you have any other questions, just ask me and I'll try to help!
Have fun with your new device!