Layouts are an advanced feature that allows you to create multiple cards based on the same information, but presented in different ways.
The most common use for layouts is to create one set of flashcards that presents your information Front-to-Back, and one set that presents the same information, but Back-to-Front. Because this case is so common, it's built right in to AnkiApp. Every deck you create comes with a Layout called "Front-to-Back" and one called "Back-to-Front".
By default, the Front-to-Back layout is selected, but you can change that with the menu accessed via the "gear" icon at the bottom of the Deck screen (see screenshot above).
The Layouts option on the Deck screen menu will show you all of the Layouts in your current deck, and allow you to create or edit new ones. Be forewarned: creating and editing layouts requires knowledge of HTML and CSS, so if you don't know what those terms mean, you may find the Layout screen confusing.
To view all the Layouts in a deck, and create or edit existing layouts, use the "Layouts" menu item on the Deck screen. It brings you to the Layouts screen, shown below.
To create a new Layout, use the New button. That takes you to the Layout screen, shown below.
There's a lot going on, on this screen, so you'll need to scroll down to see all the available options.
The Layout screen has 6 sections: