The F-1 visa is the most common student visa and is issued to full-time students enrolled in an academic or language program at a U.S. institution. In order to apply for the F-1 visa, students must first receive their USC I-20 from the Graduate and International Admissions (GIA) office. The I-20 is a three-page form with a USC official’s signature on pages 1 and 3.
Most of your questions related to the I-20 are answered here.
Be sure to check out the Office of International Services website for additional information and resources for international students.