Always check each individual university’s policy on their website as none of these are standard and a university can adhere to whatever policy it chooses!
Early Action (EA)
You apply Early and get the decision before the New Year (in most cases). You don’t have to make your decision to accept the school back until 1 May*, and once, presumably you’ve heard from your Regular Decision (RD) schools.
Early Decision (ED)
Apply Early and get the decision before the New Year. Binding. You must be ready to attend if you are accepted. You can only apply to one ED school and in most cases – check your ED school’s policy – can apply to other EA schools. But, if you get in, notify and retract your applications from all of your EA schools (and RD if applicable).
For the record, you can only apply to one ED school. You sign an agreement saying that you have done so and that, if accepted, you will attend said university. There is no question about doing this as your ethical reputation is on the line and you commit fraud by signing such an agreement and not abiding by it. Your parent agrees to this. Your counsellor also agrees to this and will send only one transcript to one ED school on your behalf. If, for some reason, this is misunderstood or your counsellor is not aware of how this works and agrees to send a transcript to more than on university for ED, the university will find out. Many other universities will inevitably find out. Admissions officers from different universities talk… a lot. You will forever put fellow classmates from your school at risk for attending that institution as the Admissions officers will look at your high school with an untrusting eye in the future.
Early Decision 2 (ED2)
Restrictions are the same as for ED(1) above, but the deadline is later and notification is therefore later. This allows a student to, presumably, apply to one school ED, and if she/he does not get accepted, go for ED2 at another school. Confused yet?
Single Choice Early Action/Restricted Early Action (SCEA/REA)
Apply Early and get the decision before the New Year. You may not apply to another school Early Action. In other words, like ED, you apply to just one school EA, but unlike ED you are not bound to attend if you get in. You can still go through the RD round and take your decision on 1 May*.
*1 May is the agreed-upon deadline by all universities that students must “accept back” and inform their institution if they are going to attend, with a deposit. This does not pertain to ED accepted students.
This is the fifth in the series of excerpts from my book, “The International Family Guide to US University Admissions”. You can read a review of the book here.