ESTA (Electronic System for Travel Authorization) and a U.S. visa are both documents that allow foreign citizens to enter the United States, but they have some key differences:

1. Eligibility: ESTA visa is only available for citizens or nationals of Visa Waiver Program (VWP) countries who are traveling to the United States for tourism or business for stays of 90 days or less. If you’re coming to the US for other purposes like study, work, or permanent residence, then you would need a different type of visa and can’t travel under the VWP. A U.S. visa can be obtained by any foreign citizen, regardless of their country of origin.
2. Application process: Applying for an ESTA is an electronic process that can be done online. You are required to fill in the application form and pay the fee. A U.S. visa typically requires an in-person interview at a U.S. embassy or consulate and usually takes longer to process.
3. Validity period: ESTA is generally valid for two years or until the traveler’s passport expires, whichever comes first. A U.S. visa is typically valid for a longer period, typically up to 10 years for a nonimmigrant visa, depending on the type of visa and the individual’s circumstances.
4. Purpose of travel: ESTA viza is only issued for tourism or business purpose stays of 90 days or less. A U.S. visa can be issued for a variety of purposes, including tourism, business, study, work, or permanent residence.
5. Admission decision: The final decision for an ESTA is still made by the Customs and Border Protection (CBP) officer at the port of entry, who will determine the length of stay. A visa holder is pre-approved for entry and has a higher chance of successful entry into the US.

It’s important to note that ESTA is not a visa and it is not a guarantee of entry. It’s a pre-screening process for travelers from eligible VWP countries to determine if the traveler is eligible to enter the US without a visa, but the final decision is made by the CBP officer at the port of entry.