What is the hose coupling

The hose coupling is a connector on the end of a hose to connect (or couple) it with another hose or with a tap or a hose appliance, such as an irrigation sprinkler. It is usually made of steel, brass, stainless steel, aluminium or plastic.

（source：http://www.kg-machinery.com/news/what-is-the-hose-coupling.html）