What is the purpose of the flash suppressor on the M-4 Carbine?

A flash suppressor is intended to dissipate muzzle flash so as not to hamper the firer's vision in low light conditions.

Sometimes, a muzzle brake is mistaken for a flash suppressor. A muzzle brake vents gases from the barrel in a direction intended to counter the recoil of the weapon, thus making it more controllable. However, a flash suppressor does not function as a muzzle brake, nor does a muzzle brake function as a flash suppressor.