Guttering

The main purpose of a rain gutter is to protect a building's foundation by channeling water away from its base. The gutter also helps to reduce erosion, prevents leaks in basements and crawlspaces, protects painted or stained surfaces by reducing exposure to water, and provides a means to collect rainwater for later use.

Rain gutters can be made from a variety of materials, the most common being PVC

Water collected by a rain gutter is fed, usually via a downpipe,  from the roof edge to the base of the building where it is either discharged or collected. Water from rain gutters may be collected in a Rain barrel or a cistern.

Materials

A rain gutter may be a:
Roof integral trough along the lower edge of the roof slope which is fashioned from the roof covering and flashing materials.
Discrete trough of metal, or other material that is suspended beyond the roof edge and below the projected slope of the roof.
Wall integral structure beneath the roof edge, traditionally constructed of masonry, fashioned as the crowning element of a wall.