Operator
The operator is the electric motor unit that drives a garage door open and closed automatically, typically controlled by a remote handset, keypad or smartphone app.
UK power-operated doors fitted with an operator must comply with BS EN 12453, including force limitation so the door stops or reverses if it meets an obstruction, and a log book under BS EN 12635. Operator repair or replacement typically costs £180–£500.
UK vs US usage
US content universally calls this component the "opener" — UK trade and technical usage is "operator", and "opener" should be avoided throughout.