This one is an animated gif of rapper Birdman / Baby rubbing his hands together in anticipation as he walks towards a door. He is one of the co-founders of Cash Money Records. This particular reaction gif is extremely popular and it is often used with a sarcastic title such as:
"How I feel when I'm walking into McDonalds with $5 in my pocket."
This is generally used whenever the person using the gif feels like "a boss" as they enter some place.