More info about the WPMU DEV badges in Profile

"Your reputation" section of Profile has "Your badges", but I don't know what each badge is for and how to get more and why I should care about having them (other than everyone always wants more of everything).

Maybe there's an img title tag, but that doesn't show on iPad.

Is there a Legend somewhere I can reference? Or can each badge have a caption?

How did I get each one?
What date did I receive each one?

Thank you.