(1) Your post is about Mail.app. If you provide specific details when you post a question, you're more likely to get useful answers.
(2) The 'pointer' is called a 'disclosure triangle'. It indicates that the item contains other items, which will be shown if you click on it. "Trash" is a actually a virtual mailbox, which contains messages deleted from your e-mail accounts, as well as from mailboxes stored on your mac. It appears that you have two e-mail accounts, "Scooperdude" and "gmoorer".
(3) I suspect you tried to move one or more mailboxes into the "gmoorer" trash. It's not a good idea to try to manipulate messages and mailboxes in Mail the way you do in Finder. If you want to delete messages, select the messages and press the Delete key, or choose Edit > Delete. If you want to remove messages from Trash, click on Trash to display its contents, select the messages, then choose Message > Move To, or Copy To, or Move to… Again.
(4) What to do. First, click the "gmoorer" disclosure triangle. Find out what is in there; it's probably another mailbox stored on your Mac. Move it back to its proper location. Then choose all mailboxes listed under "MAILBOXES", including Trash, and choose Mailbox > Rebuild. If this is successful, try to delete a message as indicated in (3).