Part of a building's water discharge system. It is a trough or channel that runs around the perimeter of a roof, and collects rainwater runoff from the roof, discharging it, usually to rainwater downpipes which convey it to a drainage system.
During rain, water rolls down from the slope of the roof to the gutters. As the water pools, it travels through the gutter system to the downspout. Downspouts carry water from the gutters to the base of the house