If you're coming to the U.S. for business or pleasure, you will need either a B-1 or B-2 visitor visa. These visas are only valid for a maximum of six months, so to stay in the U.S. longer, you must apply for an extension. Extensions give you up to an additional six months, but once your visa expires, you must leave the U.S. To re-enter, you have to apply for a new visa in your home country.
B-1 Visa for Business
If you want to travel to the U.S. on business, you must apply for a Business Visitor Visa, or B-1 visa. Perhaps you're traveling to the states to complete final negotiations on a business contract, meet with American business associates, settle an estate or attend an educational, scientific, business or professional conference. If you are outside of the U.S., you must apply for a B-1 visa at the U.S. embassy or consulate in your home country. If you are already legally in the U.S. on a different visa, you can ask the U.S. Citizenship and Immigration Services to change your visa to a B-1. Your B-1 visa will be valid for up to six months.
B-2 Visa for Tourism, Pleasure or Medical Treatment
If your trip to the U.S. is recreational, apply for a Visitor, or B-2, Visa. The U.S. Department of State considers a variety of activities to be recreational in nature, including visiting friends and family, spending vacation or holiday in the states, participating in unpaid, amateur events or contests like a marathon, and even receiving medical treatment. As with B-1 visa applicants, you must participate in a visa interview at the U.S. embassy or consulate in your country or request to change your status to B-2 with USCIS if you are already in the states. If granted, your B-2 visa will also be valid for up to six months.
Leaving and Re-entering the U.S.
When you arrive in the U.S., a Customs and Border Protection official will provide you with an I-94, Record of Arrival-Departure. You must leave the U.S. on or before the departure date stamped on your I-94. If you want to stay in the country longer, you must ask for an extension by filing Form I-539, Application to Extend/Change Nonimmigrant Status, with the USCIS. This must be done prior to your departure date, preferably as much as 45 days before. You can get an extension for up to an additional six months. If you don't apply for an extension or your extension request is denied, you must depart the U.S. If you remain beyond the visa expiration date, you will be deemed "out of status" and can be deported. To return to the U.S., you must apply for a new visa at a U.S. embassy or consulate in your home country.
Deportation Typically Not Sought While Decision Pending
If you requested an extension but didn't receive a decision from USCIS before your departure date, USCIS is unlikely to deport you until after a decision is made. This means that, although out of status, you are generally free to remain in the U.S. while your application is pending. However, keep in mind that whether or not to deport you is within USCIS's discretion, so although unlikely, it is still possible.