What exactly is Sw-e-at?

I just joined Social Work in mid-October and I'd like to know more about "Sw-e-at".  I always see it in the hot tags, and when I clicked on that, the word "sw-e-at" is just mentioned as a part of a post.  Was it a challenge?  Is it a class?  I find it intriguing and I'd like to know more about it.