These include other titles by the same author you're currently reading, more books based on titles you've recently read, and personalized recommendations based on books and genres you like to read. There is a shortcut to the Library right on top, but everything else is just recommendations based on your reading habits.
Most users might not come to this screen unless they want to explore new titles. The Home tab on the other hand is just a list of recommendations. You can also filter by type – choose between books, samples, documents, comics, and more. Tapping the filters button in the top-left corner will let you sort books by downloaded, read, or unread. There's also an option to view titles as a grid, list, or collections. The books are presented in a vertical scrolling list, but you can also tap the sorting button in the top-right corner (three stacked lines) to sort books by most recent, title, author, publication date, and more. So what's the difference between the two tabs? The Library tab is just what it says – it's the complete library of every e-book you've purchased or downloaded. The Kindle home screen has separate views for Home and Library.