Applying for Visa

WHEN YOU ARRIVE IN THE U.S. CUSTOMS

When you arrive at your port of entry in the U.S. Show your passport, visa, and the I-20 form to an immigration official.
Upon your arrival in the U.S., you should be given a small white card; "I-94." stapled inside your passport. This is your "Arrival/Departure Card.".

This I-94 card indicates your status (usually F-1).
Some I-94 cards indicate a specific date by which you must leave the U.S. Other cards are marked D/S (Duration of Status)
D/S means that you may stay in the U.S. until you complete your studies.