Favorites = Contains any content (e.g. study set, question set, folder) that you favorite. Useful for bookmarking specific content that you want to study or come back to.
Recent = Contains any recently studied content from the last month, ordered by the last time you accessed it. Useful for quickly jumping back into something you were learning.
Created = Contains all content (e.g. study set, question set, folder) that you have created. Useful for viewing your personal content, but can be unwieldy if you create a ton of stuff. If you are going to be creating dozens or hundreds of items, it's recommended that you group them in folders and "favorite" those folders to come back to.
My Study-Packs = Contains any premium Study-Packs that you have access to, whether as part of lifetime access, a free trial, or subscription.
Shared = Contains any content where you have been granted special access. For example, if someone has given you "edit" privileges on their content, or "view" privileges on private content.