Citizens of certain countries may not require a U.S. tourist visa if the trip is less than 90 days. This is known as US Visa Waiver Program; however, there are certain criteria that need to be fulfilled in order to qualify for the VWP. Not all countries participate in the VWP, and not all citizens of participating countries qualify for the VWP.
Instead, if you wish to visit the U.S. for more than 90 days, you may require a Visitor Visa, which is also known as B2 Visa. Visitor visa is a non-immigrant visa issued to people entering US temporarily for pleasure, tourism, or medical treatment.
Visitor visa is also known as B1/B2 visa and it is subject to approval. Just as all non-immigrant visas, you must apply and get the visitor visa stamped in your passport.
Tourist visa B2, is granted for a specific purpose only such as tourism, medical treatment, etc., so if you’re entering the US with this visa, you should not be involved in study, business or work. Instead, if the purpose of your trip is business, you may apply for a B1 Visa (US business visa).
As for the length of stay in U.S. with this visa, can be 6 months or even less, which is subject to grant at the port of entry at US airport on arrival.
The tourist visa does not allow to work, and violators may be subject to deportation from the U.S.
In order to obtain a Visitor Visa, each applicant must have a valid passport, submit the application form, pay the fee, and appear for the visitor visa interview at the nearest applicable US consulate in their country.