Early Action is often confused with Early Decision, for obvious reasons. They're actually pretty different, though. For a refresher on what Early Decision is, click here.
Early Action is just like regular admissions...only you do it earlier. You have an earlier deadline, and you get an answer back early. Whereas most regular application deadlines are somewhere around January 1, most Early Action deadlines are around October 1. And instead of getting a decision back in March, you get it in December. It's not Early Decision--you aren't committed to going to the school if you get accepted. You have until May 1 to make your decision, and you're welcome to turn them down even though they accepted you Early Action.
So why do colleges even offer this option? What's in it for them? It helps them spread their work out more evenly. Instead of going through applications and making decisions in one giant batch from January to March, they can knock some of them out earlier from October to December. There are plenty of seniors who can finish their applications early and be done with them, except basic human nature mixed with habitual procrastination makes them wait until the deadline. So if you give them an earlier deadline, then they'll get them in early.
It also helps them spot the applicants who really have their stuff together and who are really excited to go to their school. I worked for several years at a high school where we gave extra credit on major essays and projects if they were turned in early. A research paper, for example, that was due on Friday could get five extra points if it got turned in by Tuesday. The students who got their paper in early were invariably students who were going to get a good grade anyway. Nobody ever gave me an F paper early to make it a C-. But I got a whole lot of A papers early because they saw it as a way to get an A+. The same concept applies to applications. The students who turn theirs in several months early are demonstrating that they're organized and interested, so it helps admissions officers spot some of the better candidates.
It also helps admissions offices with their yield targets. Though EA applicants aren't quite as committed as ED applicants, because ED applicants literally have to commit to going there if accepted, EA applicants are still a good bet. If they know enough about the school to want to apply early, then they're strong candidates. And while the colleges don't get to "lock in" students who are accepted Early Action, they still get a few extra months to recruit and persuade the accepted students to enroll.
Why would you want to apply Early Action? What's in it for you? Just like the colleges, you get to spread your work over more time. If you get accepted Early Action, you may still want to apply to other schools so you can compare financial aid packages. But you'll have the confidence of knowing that you're already accepted somewhere. If you get deferred Early Action (that means they don't accept you early, but they say they'll reconsider your application with all the regular applications later) then you know that you may need to expand the number of schools you apply to and think more carefully about choosing some safety schools. Of course, if you get accepted Early Action, you can treat it just like Early Decision: not apply anywhere else and be done with it. This will give you more time and less stress in the spring.
Each school is different, but in general the acceptance rates for EA aren't higher than regular admissions rates. So if you're applying EA to "increase your odds" then you're probably going to be disappointed.
With Early Action, you have to be careful about the rules and stipulations. While most ED agreements are pretty much the same, there's a lot of variety to Early Action agreements. Some schools will gladly let you apply EA to their school and to as many other schools as you want. Others will ask you to verify that you're only applying Early Action to their school, though you're welcome to apply regular decision to as many other schools as you like. Others, like Stanford and Harvard, allow you to apply Early Action to other public universities, but not private ones. With Early Action, it's important to read all the rules of the agreements and make sure you're following them. This is too important to risk messing up and finding your acceptance rescinded.
Is there another term you'd like to see in The Glossary? Let me know, and I'll explain it!