explain me about the contactor works with examples. if i want to control a motor with contactor. and how i can use contactor in loops with over load and circuit breakers.

metres

A definite purpose contactor is designed (and rated) for a specific load. So a lighting contactor is one example of a definite purpose contactor. A motor starter contactor is another example. So, a lighting contactor is a definite purpose contactor, but a definite purpose contactor is not necessarily a lighting contactor (it might be a motor starter, for instance).

No, you definitely cannot.

The coil in a "Contactor" is essentially an electromagnetic coil that provides the driving force to close the contacts in a Contactor. When the "Coil" is energized by a lower control voltage usually from some type of controller such as a PLC, the Normally-Open contactor will close or in the oposite case, the Normally-Closed contactor will open.