Strange transfer of mechanical power

I am wondering the applications for this and what to call it so I can search online and learn more about it I was testing two of the exact same motors I found someone threw out electric scooters the wiring was a mess so used jumper cables to hook up a car battery to the pigtails coming off both motors I noticed one had a stiff spot in the chain so I unhooked the negative cable from the battery and started working the wheel around by hand to free up the chain when I noticed the other motor was turning the exact same speed as the one I was physically turning with only the positive cable on the battery my questions are what is this called and second does it drain the battery I am imagining a third motor turning one wheel and forcing the other to do same work may be a use for that in variety of projects including causing downward motion to force upward motion but I don't know what key words to type in to do a proper search

I am wondering the applications for this and what to call it so I can search online and learn more about it I was testing two of the exact same motors I found someone threw out electric scooters the wiring was a mess so used jumper cables to hook up a car battery to the pigtails coming off both motors I noticed one had a stiff spot in the chain so I unhooked the negative cable from the battery and started working the wheel around by hand to free up the chain when I noticed the other motor was turning the exact same speed as the one I was physically turning with only the positive cable on the battery my questions are what is this called and second does it drain the battery I am imagining a third motor turning one wheel and forcing the other to do same work may be a use for that in variety of projects including causing downward motion to force upward motion but I don't know what key words to type in to do a proper search

Sounds like you made a motor / generator pair. You likely had both motors connected with your positive battery lead, and possibly they were grounded through the negative or a common frame connection. But either way, physically turning the one motor made it a generator and the other motor was still acting as a motor, so it turned in response.

I've experienced similar a few years ago when hooking up some stepper motors. Had a long length of 4-conductor cable, but didn't know exactly what I'd need for each stepper. So I decided to hook a stepper motor to each end of the cable. In this configuration I could turn either stepper and the other would respond with approximately the same movement.

Ultimately, I installed the steppers, cutting what ever length of cable I needed for each, and recovered the unused 'middle' section of the cable.

many permanent magnet motors are made in a style that allows them to be used as a motor or a generator.

Stepper motors are a good source for motors to experiment with. Like a unit from a large business copier.

Connecting two motors so you can turn one of them to make the other one spin can also be called a servo-synchro pair.

probly regen power because thats what would be turning motor.
its likley earthing through chassis or whatever they attached to