A citizen of a foreign country who wishes to enter the United States must be in possession of a valid unexpired passport issued by his or her country of citizenship. This individual may apply for a visa, which is placed on his or her passport. This may be done at the U.S. Consulate having jurisdiction over the place of residence of the individual seeking a visa.
It is also important to know that there are generally two types of visas: non-immigrant and immigrant visa. A non-immigrant visa allows an individual to travel to the U.S. for a temporary period of time while the immigrant visa allows an individual to reside permanently in the United States. Note that under the visa waiver program, some foreign nationals may be eligible to travel to the U.S. without a visa, in the event they meet the necessary requirements for this type of entry.