DOF (degrees of freedom)

Every joint that can rotate or slide in one way adds one degree of freedom. A human arm has about seven, which is why it can reach around obstacles. A simple six-axis industrial arm has six, and a humanoid can have 20 to 40 across the whole body.

When you compare robots, more DOF means more flexibility but also more motors, more cost and harder control. For palletizing boxes four or five DOF are enough. For a humanoid that should open doors and carry items, look at arms with at least seven DOF and check whether the number includes the hands.