On the left-hand side of the Zimbra Web client interface are your folders, searches, tags and Zimlets.
Unread Message Count. The number in parentheses next to each folder is the number of unread messages contained in that folder. Tags folders display unread message count as well. Any item with unread messages is bold.
Inbox is where new mail is placed by default.
Sent contains messages that you have sent.
Draft contains composed messages that have not yet been sent.
Junk contains messages that have been marked as spam either by you or by the system.
Trash contains items that you have deleted.
Folders that you have created follow. If your mail account was migrated from another mail system such as Microsoft® Outlook, you may see extra folders here that represent folders on the previous mail system.
This area contains search queries that you created and saved for future use.
This area shows the tags you have created. Click on a tag to quickly see all messages that are tagged with that tag. See Using tags to classify mail messages for more information.
Zimlets are created as a mechanism to integrate third-party information and content with the Zimbra Web Client features. Zimlets let you interact with different content types in your email messages. Depending on your configuration, you may not have access to Zimlets from the Overview Pane.