Some of you may very well already know this but others may not. There is another post covering one of the tags but it only covers one of them. This post is here if you get confused about what they are, or what they mean.
A profile picture tag is a little banner in the bottom of the picture that has a word on it. This is automatically put there by the site and isn't in the actual profile picture of the user. (so, you can tell when somebody has a fake tag.)
Here's an example:
There's five different profile picture tags. The two that you see the most are MOD and SENIOR. If you scroll to the very back of the member list, you'll see some members with the tags FRESHMAN, SOPHOMORE, and JUNIOR. These are the very uncommon ones that you most likely will never see around (since most of the original 2010 members don't come on anymore).
Now that you know what all the tags are, here's what they mean:
I hope this helps. Happy holidays!