MBPs have a fan. It's positioned to vent the hot air up across the front of the screen. The air intakes are usually thin slots along the sides. It's the Macbook w/ Retina screen (not to be confused with the discontinued Macbook, the Macbook Air, or Macbook Pro w/ Retina) which has no fan.
If this is an older MBP, you may just have dust built up on the fan and in the vanes of the heatsink. Turn the laptop off, take it outside, and try blasting some compressed air into the fan. If you see dust fly out, keep at it until no more dust comes out. Be careful not to spin the fan at too high an RPM with the air. Then turn the laptop on and see if that helped.
If it helped, but not as much as you were hoping, there may still be dust inside. Unfortunately, Apple doesn't put vent holes on the bottom of the case. You'll have to open it to gain access to the insides and blow away any dust that's accumulated.
If it's a newer MBP (anything that shipped with a SSD), those are designed to be pretty much non-user serviceable. You can try the compressed air trick, but you'll have to take it to an Apple store for a more thorough cleaning.