This is an animated gif of Jay and Silent Bob dancing. Jay and Silent Bob are two fictional characters that are played by actors Jason Mewes and Kevin Smith.
The duo are mostly famous for their movie "Jay and Silent Bob Strike Back", which was released in 2001. The movie has been described as an action adventure stoner comedy. It follows both characters as they try to reclaim royalty money from a movie that has characters based on their own.
This particular gif is often used whenever some good happens and the poster is wanting to express how happy he / she is. For example "I got a pay rise at work".