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
we played. . .and shit. ."
"yoo! guess what! i just saw this
girl! and she was hot and shitt"