SCEA or REA is Single Choice Early Action or Restrictive Early action. This is where you are allowed to only apply to one private university early. Examples include Stanford, Harvard, Yale, Princeton
EA: This is just early action. You apply earlier and receive your decision earlier.
ED: This is a binding option. It stands for early decision. You apply early, get your decision early, but if you are accepted you are legally bound to attend (unless there are extenuating financial circumstances). This is typically for your first choice.