EARLY DECISION (ED) plans are binding. An ED applicant agrees to attend the college if accepted. A student may only apply to one school ED. A student who applies to a college "ED" should be 100% sure that if accepted, that is the "RIGHT FIT" college for them and believe that they can afford to attend that college. (In some cases, colleges do not offer the Financial Aid package at the same time as admissions, though the trend is to do so.)
Although students can apply to only one college for early decision, applying to other colleges through the regular admissions process is allowed. If a student is accepted by the first-choice (ED) college early, all other applications must be withdrawn. Be certain that you understand the college's ED policy, including their expectation about meeting financial need before choosing that as an application option.
EARLY ACTION (EA) applications are not binding. Normally, you may apply to several schools EA and you will receive notification of acceptance earlier than the regular decision pool. If you are confident in your application profile/grades, etc. this may be a good option. If accepted, an EA applicant can choose to commit to the college immediately, or wait until the spring. Under these plans, a student may also apply regular decision to other colleges.
Be sure to read each college's policies regarding applying Early Action to their school. Some schools are restricting the number schools a student may apply EA to (i.e. think Stanford and some of the Ivy League schools), so be sure you understand their restrictions before choosing how to apply! This practice may be called "REA" (restricted early action).
Is the ED and/or EA choice right for you? The applicant pool for early decision and early action is discriminating and self selecting. If a student’s record is not superior in every way, he/she should devote their energies to strengthening it and consider applying regular decision.
Note that some early decision and early action schools who do not admit a student in the early admission may NOT defer their application to regular decision, and will "deny" the applicant. In other situations, a school may elect to move your EA application into the regular decision pool. In this case, they are simply saying they are not ready to make a decision on your application and they want to consider your application within the bigger pool of regular decision applicants. In this case, they may also want to see first semester senior grades. Ask the college rep/admissions about their deferral process.
On the flip side, early admissions programs CAN BE very advantageous to college applicants, depending on their profile and situation. A high school student who is sure of where they want to go to and whose application profile is strong can potentially benefit* from applying via Early Admission.
*A good question to ask a college rep/admissions is the % of the freshman class that are typically admitted via “early decision/early action”.
Regular Decision: This is usually a later application deadline allowing students more time to complete applications. Students are often notified in March or the beginning of April of their admission decisions.
Rolling Admissions: Some schools offer rolling admissions meaning they accept applicants as applications are received and reviewed. Typically admissions responses are received sooner at the beginning of the application cycle. If a student applies during the "crunch time" (i.e. late fall) turnaround time to receive an admissions decision might be a bit longer.