Basiclly you press start button which powers the coil which then pulls in the contactor once the contactor makes the feed from the stop button holds the coil in untill the stop button is pressed which breaks the circuit.
Start stop circuit contactor.
See image below for an example of 3 wire control being used to pull in a contactor to start a 3 phase motor.
Note that one one of the contactor acts as a switch for the start button.
Common relay contactor set up utilising a start stop circuit fig 2.
When you press the start button and the stop button is not pressed the 24vdc relay energizes and it pulls in the r1 contactor that feeds three phase power to the motor.
Step by step procedure for the basic stop start control wiring and diagram on a magnetic contactor with nc and no push button switch and how does it works.
The contactor is operated by the control circuit energizing a coil as in the example above.