People who come from other countries, including visa waiver countries, that wish to have a visa to visit the US must apply at the US consulate, preferably in their home country, using the Department of State electronic form and thereafter scheduling an appointment.
The B visa is for temporary purposes. All who apply are considered to be intending immigrants until they prove otherwise. This means that you must prove the purpose of your visit as well as convince the consular officer that you will return to your home country after your temporary visit. You can show that you have employment, a home, family and other ties to your home country such that you have good reason to return there as opposed to remaining in the US.
In general, B-2 visits are granted six months of stay upon arrival, although the maximum is one year. B-1 visits are granted 90 days. The Customs and Border Protection officer at the port of entry is the one who decides how long to admit a visitor. While many B visas are issued for five or even 10 years, that does not mean you are authorized to stay in the U.S. for this entire period of time. It means you can use it over the course of five years but that the length of time you can stay during each visit is determined by the Customs and Border Protection officer at the time of entry. The length of time one can stay is recorded on the I-94 available electronically at https://i94.cbp.dhs.gov/I94/#/home where you can also see a history of your non-immigrant travels.
Some general purposes for using the B-2 visa are: tourism, medical procedures, touring universities, visiting family, short study courses and amateur performances for sport or entertainment. This list is not exhaustive but gives a general idea of the most common allowable purposes.
The B-1 category has many more purposes. Some are visitors who come to the US to engage in business negotiations, conferences, meetings, some religious leaders, volunteers, meetings of boards of directors, private crewman (yacht), prospective investors, domestic workers of non-immigrants or US citizens who normally live abroad, workers making installation of machinery pursuant to a contract, airline workers and others. Any sort of visit for which the purpose is business based but does not necessarily involve productive work with pay in the US could qualify for the B-1.
The B visa cannot be treated like a green card or residence permit and if you enter too frequently, stay for a long period of time, or stay out of the US too little time between visits, the visa can be cancelled and you can receive an expedited removal order at the port of entry which would bar return for a period of five years.
Visa Waiver program (WT/WB) This category allows visits for tourism and business for people from certain countries (mainly western European countries, Japan, Australia and some others) for up to 90 days without the need to apply for a visa. People who wish to visit must make an electronic application before the date of intended travel through the ESTA program. Other than sponsorship from an immediate relative US citizen or an application for asylum, there are no extensions or changes of status allowed for people that enter in this manner.
Visitors who entered using a visa and who wish to extend their stay in the US or change to another status (where permissible) must apply directly with USCIS. This involves proving that you intend to depart on the date through which you’re requesting, that you can support yourself in the US without working and explaining the need for the extension.
Finally, travelers should be aware that if you were previously deported, have a criminal record or are otherwise inadmissible, you may still be able to apply for a B visa in conjunction with a waiver.