Easter Eggers are crossbred chickens that hatcheries sell, claiming they are Ameraucanas or Araucanas. They usually carry a blue egg gene somewhere in them, usually have a beard and muffs, and usually are either a partridge color or splashy color. Of course though, since they are mutts, they can look like anything and lay any color of egg.
In most cases, if someone sells Ameraucanas, Americanas, Araucanas, or Araucana/Americanas - They're Easter Eggers. Crossbred chickens with a possibility of having colored eggs.