How does this scheme work?

Question

Electronics

Answer 1

Study the operating principle of the op-amp and everything will immediately become clear
easyelectronics.ru/operacionnyj-usilitel.html
https://www.radiokot.ru/start/analog/basics/17/
The circuit is simple.

Answer 2

it is not clear how the sensor is located.
amplifiers are turned on opposite i.e. the "+" input of one is connected to the "-" of the other.
if the sensors are illuminated in the same way, the motor current is identical.
if the sensors are illuminated differently, then the current of one motor decreases, and the current of the other increases.

Answer 3

2 sensors - when one is triggered, one engine is turned on; when the other is triggered, another engine is turned on, and the first one will not be able to turn on.