The Form I-20 is a document issued by U.S. educational institutions to international students. It certifies that a student has been accepted into a program and is eligible for a F-1 or M-1 student visa. The form includes important details such as the student's personal information, program of study, and financial support. Students must present the Form I-20 when applying for a visa at a U.S. embassy or consulate. It is also required for entry into the United States and must be kept updated throughout the student's stay. Failure to maintain an accurate Form I-20 can affect a student's immigration status.