Clean up/Organize folders within Apple Mail, Help

As you can see in the photo I've got a bunch of folders. I know my Gmail and iCloud are IMAP but how do go about organizing folders especially the Gmail.

It seems I've got 2 Deleted Messages folders, 2 Draft folders and I don't even know what a SMART MAILBOX is or where it came from.

I'm just trying to learn a little more about what I have going on here if anyone cares to comment.