A pipe union is a type of fitting used to join two pipes together in a manner that allows for easy disassembly. It consists of three main parts: a nut, a female end, and a male end. The female end typically has threads on the inside, while the male end has threads on the outside. The nut is used to connect the male and female ends, creating a tight seal that prevents leaks. Pipe unions are commonly used in plumbing and piping systems where frequent maintenance or disassembly is required. They provide a convenient way to connect and disconnect pipes without having to cut or weld them.