The power in the car comes from the batteries. The batteries are in a batteries holder. About 5 of them. Two cables are connected to the batteries holder. It is very important to identify which of those cables is the plus and which is the minus.
We have two power sources (batteries) - one power source is for the controller, the Raspberry PI, and one power source is for the motors. What is the separation between the power sources and why it exists? Why do we need two power sources? We need the different power sources because there is not enough power otherwise.
We've just plugged in the power bank in the Raspberry Pi controller. Has it started? Is it doing something? Why is it not moving? Simply put the raspberry power a small red diode and it just emits light. Well, it's on, but it will do nothing else.