Relays are used to control high amperage electricity. A switch is wired to the coil of a relay and uses very low amps to turn on the electromagnetic switch inside of the relay. The relay has contacts that handle high current and a switch that closes internally that closes when the electromagnetic switch is turned on by the round switch in this video.
The contacts in a switch are weak and won't last long from high current usage but the contacts in the relay are heavy duty by comparison and will last for thousands of cycles or more without burning up from the contacts closing which causes micro arcs that eventually burn up contacts.
Thus we are using a low amperage switch to turn on an electromagnetic switch that in turn switches a heavy duty internal "switch" with heavy contacts that allow for higher current flow. 😳
