The Documents option gives you access to the documents in your content library.
When you click on Documents, the content library appears showing the first level of folders: Work and Personal.
Those two folders are special system folders that cannot be modified.
Work includes all the documents related to the Work application, which includes cases, processes, and tasks documents.
Personal is a special folder only for the current user. It provides a personal space to organize your documents.
Clicking on the folder name or double-clicking on a folder row opens the folder and displays the current content.