What does all that mean?

EA (I or II) - Early Action - this means you are choosing to apply in the very first round in the hopes of securing admission. The acceptance is NOT BINDING. Therefore if you change your mind and do not choose to attend this school, you are fine.

ED (I or II) - Early Decision - This means you are asking the school to consider you application in the early round and if they give you admission, and meet you demonstrated need, you promise to attend. If you do not get sufficient aid, you are not obliged to attend. You may turn down the offer and accept the other.

REA - Restrictive Early Action - This is the offer that many of the Ivys use. You are applying early, you are not obliged to attend, but you promise that you are not submitting any other early applications. 

Sometimes a student may develop a plan where they have the ED I for their dream school, the ED II for their second choice and the EA for a safety.  The REA makes that impossible.