There are many different usa visas available. Therefore it is very important that you figure out, which visa is the right one for your stay in the United States.
If you are visiting the USA for touristic reasons only, you have the following usa visas options.
As a business traveler (B-1 Business Visitor) or tourist (B-2 Tourist Visa), it allows you to stay in the country for up to 180 days at a time or to enter the country multiple times during a year. Usually those visas are valid for ten years, but can also be limited to a shorter period of time.
Since 1986 citizens of certain countries do not require usa visas to enter the US anymore. They now have the possibility to travel under the so-called Visa Waiver Program (VWP) that allows them to enter the US as a tourist for a maximum of 90 days a year, or transit the US.
People who want to work or study in the USA, should carefully check all usa visas which are available in this category. Keep in mind, that those visas are non-immigration visa, meaning that they are only valid for a couple of years and do not permit you to immigrate to the US.
Last but not least, there are different immigration usa visas available. For many people, applying for a permanent residence permit is the most important step towards living and/or working in the US.
Immigration visas, the so-called "green cards," permit foreign citizens to live and work in the US without being limited to one specific employer.
There are a number of ways to obtain a green card. The basic categories are employment-based and family-based visas, and the green card lottery.
If you are planning a trip to the USA, you should check all usa visas options up-front or get a personal counseling by visa experts.