A sewer is an underground system of pipes and conduits that transports wastewater from homes and businesses to a treatment facility. The term 'sewer' can refer to the entire system, or to individual components such as a GUTTER, CONDUIT, PIPE, ORACLE, DRAIN, RAT, and MAIN. A GUTTER is a channel along the edge of a roof that collects and directs rainwater away from the building. A CONDUIT is a PIPE or tube that carries water, gas, or electrical wiring. A PIPE is a hollow cylinder used to transport fluids. An ORACLE is a device or system that provides advice or guidance. A DRAIN is an opening in a wall or floor that allows water to escape. A RAT is a type of rodent that lives in sewers. A MAIN is a large PIPE that carries wastewater from many sources to a treatment facility.