<Li> holding a Form I - 512 ("Authorization for Parole of an Alien into the United States") </Li> <P> Mexican citizens may travel to the U.S. without a passport under limited circumstances if holding a Border Crossing Card and seeking to enter the U.S. for less than 72 hours while remaining in the "border zone". </P> <P> While there are about 185 different types of visas, there are two main categories of U.S. visas: </P> <Ul> <Li> Nonimmigrant visa - for temporary visits such as for tourism, business, work, visiting family, or studying . </Li> <Li> Immigrant visa - for people to immigrate to the United States . At the port of entry, the immigrant visa holder is processed for a permanent resident card (I - 551, often known as a' green card'). Upon endorsement (CBP admission stamp) it serves as temporary I - 551 evidencing permanent residence for 1 year . </Li> </Ul>

How many types of usa visa are there