There are two types of folders, "My Workspace", folders that are only visible to you and "Shared", folders that are shared between your teammates.
Manual Filing
Drag emails to the folder manually to file.
Auto-filing
Set rules for each folder so that emails that match the rule will be filed automatically to that folder.
5.3 Removing an email
To remove an email from a folder, select the email and click on "Remove from folder".
5.4 Opening a folder tab
To open a folder in a new tab, right-click on a folder and select "Open in a new tab". Maximum tabs that can be opened at one time is 10.