Line sensor wire gauge questions

[Dinush]

I was also unsure because I soldered the blue wire in the line sensor to a PWM pin which connects to the Digitali I/O ground, but in the circuit diagram, it shows the line sensor connecting directly to the ground on the circuit breaker.

And in the rule book it says:
"Sensors may not be wired in series with their loads to directlyu control those loads"
Which is why I was wondering about running one wire from the 20amp circuit breaker and cutting off parts off the insulation and sodering the brown wire of each sensor to the +12V wire.

It also says:
"The loads must be controlled by PWM signals sent by the Robot Controller to relays or speed controllers"

What exactly is this reffering to? Does this mean that the power of the sensors has to be controlled by the microcontroller through a relay?