What is a visa? And what is visa status?
A nonimmigrant visa is a stamp/sticker that the US Embassy or consulate places on a page of someone’s passport, indicating the kind of nonimmigrant status that s/he is seeking when getting to the US. This visa stamp/sticker gives the person the right to request entry into the US in that type of status. However, the visa stamp alone does not give a person the right to enter the US, as other documents must be shown with it, and the final decision to allow entry into the US rests with the Customs and Border Protection officer.
Further, the only time that a non-immigrant is required to have a valid visa is when that person enters the US from abroad. The validity of the visa does not affect how long a non-immigrant may stay in the US.
This is the difference between a visa and visa status: the visa stamp/sticker in the passport is a document that affects how long one can request entry to the US, not how long that person may stay in that status in the US.
After being accepted to IU South Bend for a undergraduate program, Ming made an appointment and went to the US Embassy in Beijing for a visa interview. After her successful interview, she was given her passport, inside which she saw a new US visa sticker that showed “F-1” and an expiration date of one year later.
Ming showed her new visa, her valid passport, and her IU I-20 to the US Customs and Border Protection agent at the airport in Los Angeles when she entered for Fall Orientation. The agent confirmed with Ming that she was going to IU South Bend to study Business and, after stamping her I-20 and giving her a stamped I-94 card, Ming was permitted to enter the US as an F-1 student.
A year later, Ming’s visa stamp/sticker expired, but because she was properly allowed into the US as an F-1 student, Ming did not have to depart from the US as long as she was maintaining her F-1 status through full course of study and working only with proper authorization (Information about staying in status for F-1 students).
Each country has a specific agreement with the US government regarding the length of time that visas are granted. This “visa reciprocity” agreement differs from country to country. For more information, please see the State Department’s page about visa reciprocity.