Wikipedia
Fast-roping, also known as Fast Rope Insertion Extraction System (FRIES), is a technique for descending a thick rope. It is useful for deploying troops from a helicopter in places where the helicopter itself cannot touch down. Fast roping is particularly useful for marines, who can use the technique to board ships at sea as well as to reach destinations on land. First developed by the British with UK rope manufacturer Marlow Ropes, its first combat use was during the Falklands War. The original rope was a thick nylon that could be used in a manner akin to a firepole. The special ropes used today are braided (plaited), which results in a pattern on the outer circumference that is not smooth and so is easier to grip. Originally, each person would hold the rope for the next person; however this has been phased out.
It is quicker than abseiling (rappelling), although more dangerous, particularly if the person is carrying a heavy load, because the rope is not attached to them with a descender. The person holds onto the rope with his gloved hands and feet and slides down it.
Several people can slide down the same rope simultaneously, provided that there is a gap of approximately between them, so that each one has time to get out of the way when they reach the ground.