What do you call a robotic joint that allows a robot to move its arm in any direction unlike the human arm? Is there a name to such joints? I am thinking there might be several types that would allow such freedom of movement, so just pick one.
You'd have to show us a technical drawing to know which you mean exactly. One possibility is a universal joint:
This joint allows the joint to fully rotate as it bends, so it can go in any direction. A similar device is a ball-and-socket joint (or just ball joint) which does not allow rotation but does allow the mobile piece to bend in any direction.