What's the difference between contactor and relay?

1, the essential difference between relay and contactor is that the load is different, the current capacity is large contactor, small relay, there is a difference in the use of contactor in the main loop, control loop relay.
2, the role of the contactor is used to connect and break the larger current signal, drive the motor and other power equipment;
3, the function of relay is used for signal conversion, the interface between different voltage levels of equipment control signal, its contact carrying capacity is generally small, used to drive the contactor and other electrical components.