Criminal Minds is a police drama that has ran for five seasons so far. Five seasons of psychotic rapists and hit and miss puns that the general sheeple population always loves.
According to this source, the BAU is only one department of a branch called the NCAVC. (Of which I will never remember what the letters stand for and always will refer to it as Nikavik) Whether or not this is explained in any of the episodes is unknown to me. It most likely got lost to me in the flood of Gilmore Girl's speed of speech. If it is explained, I bet there's some member of the real NCAVC that feels the need to punch a puppy everytime he or she sees this show. Sort of like trying to talk to a real cop about Law and Order.
Hunting down rapists. Just, rapists, really. Psychotic rapists, normal rapists, sadistic rapists, etc, etc. If you squint a little, you may find something about just a good old revengeful murder. Why it is centered so much on rapists is not explained in any way. Watchers are just supposed to expect that everywhere they go, someone is hiding in a trashcan ready to jump out and rape them, reasons be damned. Did the creators of the show all share a grudge against their drunken, smelly Uncle in the past? We will probably never know, but we can feel pity for the poor saps that have to go through the scripts of every episode.
Well, except for this one. By just opening his mouth, most have a strong desire to see him get shot in the face.