Visa Waiver Program:

The Visa Waiver Program (VWP) enables nationals of certain countries to travel to the United States for tourism or business [visitor (B) visa purposes] for stays of 90 days or less without obtaining a visa. VWP eligible travelers may apply for a visa, if they prefer to do so. Not all countries participate in the VWP, and not all travelers from VWP countries are eligible to use the program. VWP travelers are required to apply for authorization though the Electronic System for Travel Authorization (ESTA), are screened at their port of entry into the United States, and are enrolled in the Department of Homeland Security’s US-VISIT program.

To enter the U.S. on the Visa Waiver Program, travelers must be:

• A citizen of one of the countries enrolled in the VWP, and in possession of a VWP-compliant passport.  
• Possessing the ESTA authorization   (https://esta.cbp.dhs.gov/esta/)
• Travelling for business, pleasure, or transit  
• Staying in the U.S. for 90 days or less

AND if entering the U.S. by air or sea must be:

• Holding a return or onward ticket. If travelling on an electronic ticket, a copy of the itinerary must be carried for presentation to the immigration inspector.
• Entering the United States aboard an air or sea carrier that has agreed to participate in the program This includes aircraft of a U.S. corporation that has entered into an agreement with the Department of Homeland Security to carry passengers under the Visa Waiver Program. 

If entering the U.S. by land from Canada or Mexico:

The VWP permits arrivals from Mexico and Canada at land border ports-of-entry (POEs). The documentary requirements are the same, except there is no requirement for round-trip tickets and signatory carriers, as there are no carriers involved. You must satisfy the inspecting officer that you have funds to support yourself during your stay and to depart the U.S.

Who is not eligible to use VWP:

Some travelers may not be eligible to enter the U.S. visa free under the VWP. These include people who have been arrested, even if the arrest did not result in a criminal conviction, those with criminal records (even if subject of a pardon, amnesty, or other act of clemency), certain serious communicable illnesses, those who have been refused admission into, or have been deported from, the U.S., or have previously overstayed on the visa waiver program. Such travelers must apply for a visa. If they attempt to travel without a visa, they may be refused entry into the U.S.

B1/B2 Visa

B visa category is reserved for foreign nationals who wish to enter the U.S. temporarily for business (B1) and for pleasure or medical treatment (B2). To determine whether you should apply for B1 or B2, consider the nature of your planned trip. If it is recreational, such as visiting family members, tourism, amusement, or receiving medical treatment, a B2 visa would be more appropriate. If the purpose of your travel is to attend business meetings or scientific conferences, negotiate a contract, settle an estate, etc., you should apply for a B1 visa.

Who is eligible for a B1 or B2 visa?

• Under the Immigration and Nationality Act, a visitor visa applicant is presumed to have immigrant intent. To qualify for a visitor visa, an applicant must prove to the consulate officer that s/he is not an intending immigrant, by demonstrating all of the following:
• Their planned stay in the U.S. is temporary;
• They have sufficient funds to cover all expenses;
• They have strong social and economic ties to their foreign residence and do not intend to abandon it.