Introduction: What is Differential Drive?
A differential drive system is how robots and vehicles, like tanks, move around. Instead of using a steering wheel, they have two sets of wheels(generally 1-2 in each set on each side) (or tracks) that can spin at different speeds.
Think of a tank: if both tracks move forward at the same speed, the tank moves straight. If the left track moves faster than the right, the tank turns right. If one track moves forward and the other moves backward, the tank spins in place. This is how many robots, including Roombas and Mars rovers, navigate!