All nonimmigrant foreign visitors are required to have to a visa stamp in their passports to enter the United States. A Visa is issued by the U.S. embassy or consulate abroad. A Visa is an "entry document" and cannot be obtained in the U.S.
International visitors come to the United States for various reasons and the type of visa you must obtain is defined by U.S. immigration law, and relates to the purpose of your visit. Visa types are classified using an alpha-numeric system.
There are two main visa types for prospective nonimmigrant student: F-1 or J-1.
The F-1 visa type is the most common visa used by degree seeking students in the United States.
The J-1 visa type is generally used for students in short term educational exchange programs or for international research faculty.
The Visa's expiration date does not determine the duration of your stay in the U.S. (a visa stamp is an
document only). Once you are in the U.S., the duration of your stay is determined by length of your academic program.