A pipe fitting is a fitting used to connect pipe segments, that is placed at a junction or transition in a piping system and may be used to change flow characteristics such as direction and flow rate. In this instance valves are not classified a pipe fittings, they are classified as valves.
A pipe elbow is a pipe fitting with typically two ports used to change the direction of flow between connected elements. Pipe elbows generally have a radius of curvature up to twice the diameter of the pipe.