Any authenticated user can defines its own bookmarks in the application. They are similar to bookmarks in a browser but are dedicated to link into the application and they are stored in the database (and so you'll get them from any browser you use to connect to the application. They are available through the bookmarks box, on the left of the screen.
To add a bookmark on the page you're seeing, simply click on the "bookmark this page" link in the "manage bookmarks" dropdown-menu. You'll then be asked to give it a title. Once created, it will appear in the bookmarks box.
In this dropdown-menu, the "pick existing bookmarks" link will show you a list of bookmarks already defined by the other users of the application. If you are interested by one of them, simply click the [+] sign to the left of it to add it to your bookmarks.
The "edit bookmarks" link will show you a form to edit your current bookmarks, for instance to change their title. If you are using share bookmarks (picked from another user), those bookmarks won't appear in the form unless you're allowed to modify them.
To remove a bookmark, simply click the [-] sign to the left of it.