Not all universities offer an Early Decision option, and each one might have its own fun little stipulations and rules. But the basic idea of Early Decision is that you turn in your application early, you get a decision from the school early, and if you get accepted you agree to go there and withdraw any other applications you may have also sent. This requirement that you enroll if you're accepted is why Early Decision is usually referred to as "binding." Early Decision is exactly what it sounds like: you decide early that you really want to go this school; they decide early if they're going to accept you; if they do, then it's decided--early--that you will definitely go there.
Because you agree that you'll withdraw your other applications and attend the school that accepts you Early Decision, you can only apply Early Decision to one school. If you were to get accepted E.D. to more than one school, you'd be obligated to attend all of them, and that would be really expensive as well as physically impossible. So only apply E.D. to one. But you can apply to as many other schools--so long as it's not E.D.--as you want while waiting to hear back from your E.D. school. You don't have to wait to apply to others, and you really shouldn't.
So why do colleges even offer this option? What's in it for them? They really like the safety of it. They accept you, and you show up. The people they accept in regular admission may or may not show up, because those students have probably applied to other places as well. Admissions offices have a very specific number of people they need to show up in the fall. That number is called the Yield. If not enough new students show up, then they're not bringing in enough revenue. If too many show up, then they may not have enough room or resources for them. So admissions offices go through really complicated statistical models to guess how many people to actually accept in order to get their yield. They then spend a lot of money and time trying to recruit the people they accept hoping to get them to show up. But with E.D., the offices can skip most of that, because they're really sure that virtually everyone they accept E.D. will be there in the fall. In 2017, only about a third of colleges hit their yield target, so tools like E.D. look really good to them. Last year at Dartmouth, for just one example, 47% of their class were accepted Early Decision.
Why would you want to apply Early Decision? What's in it for you? Mainly what you get from E.D. is time. And money. And less stress. So that sounds pretty good. If you're accepted E.D., you'll probably submit fewer applications. If you get accepted and you commit to a school a month before your other applications were even due, then you won't be sending--or paying fees for--those applications. And then, in the spring, when all the other college-bound seniors are getting back their decisions, possibly going on more college visits, and trying to figure it all out, you'll have figured it out months earlier and won't have to deal with it. If you feel strongly that a school is a good place for you and you like saving time, money, and energy, then E.D. might be a great option for you.
Some people will tell you that you want to apply E.D. because it gives you better odds of being accepted. That's at least superficially true, because acceptance rates are usually higher for E.D. applicants over regular applicants. But "odds" makes it sounds like some sort of random choosing, which it most certainly is not. It makes sense that Early Decision acceptance rates would be higher, because they're choosing from a pool only made up of people who want to go to the school strongly enough that they'll commit ahead of time and who are organized and on top of things enough to send out an application months ahead of schedule. If you're not a student who that school will want to accept, for whatever reason, then applying E.D. is not going to change that. If you are, then applying E.D. may be helpful--not because there's some magic to E.D., but because colleges like the safety of that commitment.
With Early Decision, you have to be very careful about money. There's a common perception that only people who can afford to pay full price should apply E.D., because you may be committed to doing something you can't afford. This isn't really the case. But you still need to do your homework. Don't apply early unless you've already filled out you FAFSA early and know what the formula says your financial need is. Make sure the university you're applying early to meets 100% of financial need (you can find this on Big Future as well as other places.) Go through the school's net price calculator and see if their estimate is something you can afford. But if you have evidence to believe that you can afford the school, then you can feel ok apllying Early Decision. If the school gives you a different financial package then the net price calculator and FAFSA-determined need led you to expect, tell them and see if they'll increase their package. Even if you ultimately realize that you just cannot afford the school, you can back out. They're not going to sue you. They're not going to chase you down and call you bad names. It will be ok. It would be dishonest to apply E.D. without a good estimate that you can afford it, but it's not illegal or dishonest to walk away from a bad deal you made in good faith.
The other money issue with E.D. is the opportunity cost. If you apply Early Decision, get in, and can afford it, you may still be missing out on a better financial aid package from somewhere else. You don't have the opportunity to shop for the best deal. A lot of students are looking for the best deal, and they should not apply E.D. But if you know you'd go to a certain school if they accept you and you can afford it, even if it's not the best deal, then E.D. is the way to go.
Is there another term you'd like to see in The Glossary? Let me know, and I'll explain it!