A foreign national who wishes to enter the US must first get a US visa, that will be placed in the foreign national’s passport or on the travel document issued by the foreign national’s country of citizenship. Some foreign nationals can enter the US without a visa if they fulfill the requirements for visa-free travel. US citizens don’t need a US visa for travel. However, when traveling abroad, they may require a visa issued by the embassy of the country they intend to visit. Under such circumstances know the visa requirements by checking the Country Specific Travel Information.
With a US visa, you can travel to a port of entry, airport or land border crossing, and you have to request permission of the Department of Homeland Security (DHS), Customs and Border Protection (CBP) inspector to enter the US. Remember that having a visa does not mean that you can enter the US. It only means that a consular officer at a US Embassy or Consulate abroad found you to be eligible to enter the US for that specific purpose. The inspectors at the port of entry are responsible for your admission to the US, for a specified status and stipulated period of time.
The type of visa you require is defined by US immigration law. It depends on the intention of your travel. There are two main categories of US visas namely immigrant and non immigrant visas. An immigrant visa is to enter the US and live there permanently. Whereas the non immigrant visa is used to travel to the US for a temporary period. If you are neither a US citizen nor a lawful permanent resident (green card holder), there are many types of non immigrant visas that will facilitate your travel to the US. The main intention of your visit and other facts will determine what type of visa you have to get. Remember to gather information about the type of visa you will need to get into the US, and also familiarize yourself with the steps required to apply for the visa at a US Embassy or Consulate abroad.