The ESTA visa waiver is a different travel authorization from a nonimmigrant visa (B1/B2).
Depending on the applicant’s nationality and eligibility status, one of the two will need to be presented to an officer at Customs and Border control when entering the United States.
B1/B2 visa holders are not required to apply for ESTA as a valid visa covers all US Customs and Border Protection’s requirements to pass through passport control upon arrival.
For travelers who are eligible for both the ESTA and the B1/B2 visa, the ESTA is quicker and easier to obtain as it can be applied for online. The ESTA application requires the individual to provide their personal and passport details and the travel authorization is delivered by email within 3 working days.
B1/B2 visa applications must be made at a US embassy and require the traveler to attend an interview and provide a number of supporting documents. Processing times are lengthier than those of the ESTA.
Additionally, successful ESTA applicants are granted a 2-year permit to enter the States multiple times for a maximum period of 90 days per stay.