You know that you need a visa to enter the United States. You apply for one, and it is granted. Does this mean you can absolutely enter the country when you arrive? Is that entry guaranteed now that you have the paperwork in order?
It is not. The government specifically warns against this mindset. Getting the visa means that officials reviewed your case and determined that it was valid. This gives you, as they put it, “permission to apply to enter the United States.”
After getting your visa, you still have to make your way to a port of entry and apply. You could fly in, for instance, making the airport where you land your port of entry. You could also cross the border on a boat, through a traditional port, or by crossing on land through one of the numerous stations where this is done legally.
You do need a visa, and it absolutely helps your case. It tells you, among other things, how long you can stay. It lays out the reason for your visit; tourists use different visas than students or workers, for instance.
But the visa does not mean they are definitely going to let you in. You still have to talk to the officials at the port of entry and ask for permission to come into the country. If they have reason to deny it, they can do so, regardless of your visa status.
Since this process can be complex, be sure you’re well aware of your legal options every step of the way.