The arm tag is intended to be used for questions relating to robotic arms from, small hobby arms with only 1 or 2 degrees of freedom to large industrial robots with complex joint assemblies. For the ARM CPU, use the tag arm-cpu.
A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; an arm may a whole robot or just a part of a more complex robot.
Robotic arms come in all shapes and sizes. Most robotic arms are described by their degrees of freedom, or "The number of independent parameters that define its configuration". These parameters traditionally refer to rotations at locations or joints, such as "Shoulder" or "Elbow" or "Wrist".
For the ARM CPU, use the tag arm-cpu.