Get this great book: Audition: Everything an Actor Needs to Know to Get the Part

This book contains great tips you need to have under your belt to give you the edge at your next audition.

Actor - An actor (or actress) is an individual who acts in a drama and who works in television, film, theatre, or radio in that capacity. The ancient Greek word for an "actor," ὑποκριτής (hypokrites), means "one who interprets"; in this sense, an actor is one who interprets a character.

More at: http://en.wikipedia.org/wiki/Actor