what exactly does the PIDcontrol do anyways?

Google is your friend. .

In short, when you set your motor to 50, the program is sending 50% power, but the motor might no be running at that power level, for instance friction and other factors are involved, so PID accounts for the difference and adds/subtracts this to the value.

Stands for Proportional Integral Derivative.

The PID is controlling the speed of the motors.
Uses the encoder to find the actual speed.

Without PID:
Your wanted speed = 40
The power motor receives = 40

With PID:
Your wanted speed = 40
The power the motor receives = 40
The measured speed = 25
Calculated difference = -15
PID extra power = 15
The power the motor receives after PID difference= 55
The measured speed = 35
Calculated difference from wanted speed = -5
PID extra power = 5
The power the motor receives after PID difference= 60
The measured speed = 41
Calculated difference from wanted speed = 1
PID extra power = -1
The power the motor receives after PID difference= 59

Continues forever

so is enabling PID control useful or not? I figured it was messing with our motors since the beginning so I turned it off.

it is useful in autonomous only if u have encoders but bad for tele op, it gives tele op a jerky feel.