what is the difference betweena contactor and a relay?

Answer 1

Hi

They have both contacts (switches).
A switch (simple on off switch) contains 2 contacts (contactors as you call them). A simple relay also has 2 contacts.

What is the difference than you might wonder? ;)
Well... a switch needs to be operated by your finger while a relay is being operated with electricity.

A relay is therefore nothing more than an electronic switch, it does the same, it only requires electricity instead of a finger to switch the contacts. It works on a small electromagnet that pulls the contacts towards each other, this electromagnet requires electricity.

I hope this helped you a bit? :)
http://en.wikipedia.org/wiki/Relay

Kind regards,
Sebastiaan

Answer 2

A relay is an electrically operated switch, designed for general purpose use on light to medium loads. A contactor is similar, but designed for much heavier load currents and often with a specific purpose in mind.