Oh! The Joys I Get From Spam!

I was just checking my Hotmail junk mail folder when this message caught my eye popped up. I had to check it out...
In big, bold letters, it said:
NASTY DOGFART SLUTS
TAKING IT HARD AS HELL!
CLICK HERE TO WATCH FOR FREE LIVE!
What does that MEAN?!!! I've been around the block a bit... I've seen stuff... but I have no idea what a "nasty dogfart slut" is nor do I understand the appeal of one. Can someone help me?