Most filtering of unsolicited automated email (aka "spam" or "junk mail") is handled by a spam filter before those email messages reach your Inbox. Mail that might possibly be junk mail, but is not certain to be junk, is placed in your Junk folder. You can review these messages and either move them out of the Junk folder or delete them. If you don't move or delete the messages, they are purged after a number of days as specified by your administrator.
If you find that you are receiving a large number of unwanted email messages, contact your administrator. Reporting mail as spam helps your email administrator to fine-tune any spam filtering that may be in use at your site.
If you find an email message in your Inbox that is spam, you can highlight it and click Junk on the toolbar. The email is moved to your Junk folder and the spam-training filter is taught that the mail is junk.
You can empty the Junk folder by right-clicking the folder and choosing Empty Junk.