Where can such a thing be used? Scope?

Question

Do it yourself

https://ru.aliexpress.com/item/DIY/32877204851.htm...

Answer 1

according to the description.
a black line is drawn on the white floor - and this trolley moves along it on its wheels.
if the trolley moves to the side - the black bar obscures one of the sensors, the circuit slows down one of the motors and the trolley returns to the line

Answer 2

You can collect in the radio club. Along the way, understanding how "operational amplifiers" work. Cats might also like it.

Answer 3

Scope: transportation of goods along a given trajectory.

Answer 4

Delivery of goods along a given route from the warehouse to the goods issuing table.