What is the thing fixed between the handlebar and the body of a folding bicycle called?

The thing fixed between the handlebar and the body of a folding bicycle is called a folding handlebar stem or a folding stem stem.

Generally, a folding bicycle consists of a frame folding joint and a stem folding joint. By folding the frame, the front and rear wheels are folded together, which can reduce the length by about 45%. After folding, the whole bicycle can be put into a cabin and a folding bag, as well as the trunk of a car. During the folding process, no external tools are required, and the bicycle can be folded and unfolded manually or folded by itself. After folding, the seat pole is used as a support point to ensure that it can stand stable after folding.