In the photo above, MARSOC operators prepare for a nighttime training mission aboard the aircraft carrier George Washington (CVN-73). This image was taken by Mass Communication Specialist Seaman Everett Allen, and is posted here courtesy of the US Navy.

This is how the US Marines define the mission of MARSOC on their website:

Our mission is to recruit, train, sustain, and deploy scalable, expeditionary forces worldwide to accomplish special operations missions assigned by U.S. Special Operations Command (USSOCOM). To accomplish that, we equip and train Marines to succeed in austere conditions against a wide range of adversaries. Marine Raiders execute complex, distributed operations in uncertain environments, achieving silent success and strategic impact.

Check out this video of Marine Raiders in action.