Something you say at the end of your sentence for a varity of reasons. Being too lazy to finish your sentence and not having an actual verb in your sentence are common causes to throw in "and shit."
Also used to make things that aren't really as interesting as you had thought in your head seem cooler.
"yo bobby's over we're playin video games and shit"
"Oh I was out with the guys.
girlfirned: What did you do?
"Oh you know we went to the bar and ..
you know the bar and shit. Hey how about that Sea Biscuit movie! wanna go see that?"