"Camouflage has been used in a variety of ways since the beginning of human civilization. One of the most popular uses of camouflage is for military uniforms, with its main goal being to hide a soldier and his gear from being seen by the enemy. Each branch of the US Armed Forces has a specific type of camouflage for their clothing, not only to differentiate between soldiers but also serving different functions. The US Army commonly uses the Universal Camouflage Pattern. The Multi-Environment Camouflage Pattern is used by the US Army in varying environments and light conditions. The Marine Pattern Uniform is used by the US Marines. The Navy Working Uniform comes in 3 variants, designated for use in woodland, desert or ship use. And lastly, the Airman Battle Uniform, which is a service-distinctive attire for the US Air Force."

http://www.specialforces.com/blog/industry-news/five-examples-of-military-clothing-used-in-the-us-military.html