The answer to 'what is drain' is a pipe or channel that carries away wastewater or other unwanted liquids from a sink, bathtub, shower, or other plumbing fixture. Drains are an essential part of a home's plumbing system, helping to remove used water and prevent backups or flooding.
Drains typically connect to the main sewer line or septic system, allowing water to flow out of the home and into the municipal sewage system or a private septic tank. Proper drainage is crucial for maintaining a clean, healthy, and functioning plumbing system in your home.