A visa is a document that allows you to apply for entry to the United States, but it does not guarantee entry. The decision to grant or deny admission to the United States is made by the U.S. Customs and Border Protection (CBP) officer at the port of entry. The officer will consider various factors, including the purpose of your visit, the documents you present, and your admissibility to the United States under U.S. immigration laws.
It is important to note that even if you have a valid visa, you may still be denied entry to the United States if you do not satisfy the other requirements for admission, or if you are found to be inadmissible for any other reason under U.S. immigration laws.
Therefore, it is important to be prepared and to have all the necessary documents and information ready when you apply for a visa and when you travel to the United States. You should also be aware of the purpose of your visit and any requirements or restrictions that may apply to your stay in the United States.
See Admissions on the CBP website for more information.