Hey you might know this. Is there a term for using what effectively a differential gear arrangement to get two axes of motion as shown in the arm in this video

Hey you might know this. Is there a term for using what effectively a differential gear arrangement to get two axes of motion as shown in the arm in this video (twice actually, for axes 2/3 and 4/5)? https://youtu.be/ri8kwOCJnY8 https://youtu.be/ri8kwOCJnY8