You now have the ability to tag other users in your posts. Works just as you'd expect it to. Tag somebody and they get a notification that they were tagged in X topic. To tag somebody just @name them. Once you post the first few letters you should get a box popping up with member suggestions, like so
If you have new mentions, it will be displayed like this
The number of new mentions you have will be displayed on the main bar. Clicking it from the dropdown will give you a list.
Old mentions should fall off this list after 7 days. If for some strange reason you want an email to be sent to you whenever you get a new mention, you can enable it from there.
And if you're using the Tapatalk app, you'll receive push notifications when you've been tagged.
Don't abuse this. Nobody likes being randomly tagged just for laughs.