If any of your chosen schools have interest, they will invite you to submit a secondary application.
Most allopathic medical schools use a centralized online application service called AMCAS (osteopathic medical schools use a similar service). It provides medical schools with enough information to make an initial screening of applicants. Your completed AMCAS file will include your undergraduate transcript, MCAT scores, information about your extracurricular activities, and a short personal statement. Some schools also allow you to submit letters of recommendation through AMCAS.
You can submit your information to AMCAS beginning in June of each year. Each medical school sets its own final deadline for submitting information to AMCAS. Regardless of these deadlines, admissions officers recommend you submit your application as early as possible.
AMCAS charges a fee for this service (aid is available to those who need it). Procrastinators take note: AMCAS is serious about its deadlines. If an application is late, you'll get it back without a refund.
After reviewing your AMCAS file, the admissions committees at your chosen schools will either reject you or send you a secondary application, or "secondary."
Some schools send all of their applicants a secondary. Others go through an initial cut that is usually based entirely on GPA and MCAT scores. Schools like to send out secondaries because they charge you a fee for the privilege of sending them back.
Unless you've decided not to apply to that school, you should complete and return each secondary application as you receive it. Most schools will reject any application that arrives after the deadline.
Secondaries typically include a variety of essays on assigned topics. You could be asked to discuss your favorite novel, describe a leadership role you've taken or detail your greatest academic achievement. You will also be asked to submit letters of recommendation if you did not do so through AMCAS.
If the cost of sending back secondaries is prohibitive, you can call the school and request a fee waiver. If you were eligible for a waiver from AMCAS, for example, you will probably be eligible for a waiver from individual schools.
Once the committee reviews your secondary application, they will do one of three things: reject you, invite you to the campus for an interview or hold your application until after the first round of interviews. Final decisions are usually made after the interview.