In the big picture, there are two broad categories of visas: temporary (non-immigrant) and permanent (immigrant).  Temporary visas are issued with a limited purpose (tour, business, study, employment, etc.), and your status in the U.S. will be limited in length as well (6 months, 2 years, until you graduate, etc.).  Permanent visas are for your permanent residence in the U.S.; once you enter the U.S. with a permanent visa, you will soon receive a green card by mail.

To apply for a temporary visa, in addition to showing the specific purpose of your visit, you also have to convince the U.S. Embassy/Consulate that you intend to stay in the U.S. only temporarily, i.e., you have no intent to permanently settle down in the U.S. and you will definitely return to your home country after this temporary visit (the only exceptions to this requirement are H-1B and L visas).  This is usually done by submitting documents showing you have strong ties
---family, social, finance, employment, etc.
---to your home country.

From the menu on the left, please select the type of temporary visa you are interested in.