Easter egger is a generic term used by people who raise chickens for a bird bred with Araucana or Ameraucana to gain the colored egg laying gene. It isn't an actual breed at all. It's just a colloquial term.

Also, Easter Eggers specifically refers to the blue gene, and creates shades from blue to green. Some birds it doesn't take well at all, and they produce barely colored eggs. Others produce a bright brilliant blue.

Other colors, like the browns, reds, and pinks, come from other breeds of chicken like marans. I've even had barred rocks and orpingtons lay browns.

Easter egger though, is the chicken equivalent of a mutt, as long as the mutt contains the blue egg gene.