A contactor is a multi-pole switch that is activated by energizing a control coil or solenoid, basically a relay that can handle more current. You find them in

A contactor is a multi-pole switch that is activated by energizing a control coil or solenoid, basically a relay that can handle more current. You find them in motor starters, you can use them to switch multiple light circuits with a single switch, among other uses. The contactor is what connects the battery to the motors to provide them with power. If the contactor is bad, power cannot flow from the batteries to the motors and the car cannot be driven. I believe the rest of the electronics are powered from a 12VDC battery, all of that would still work.