A backwater valve is a check valve that keeps drainage water from backing up into the structure. A backflow valve is in the water line to prevent water from a contaminated source from backing into the potable water.
If you have a cast iron floor drain you probably have a ball type backwater valve with threads. Cleaning the threads on the floor drain is a chore. A wire brush wheel in a drill helps but you usually have to chase the threads with a pipe dye. It is not easy to do. Be patient and allow a couple of hours.