ESTA (Electronic System for Travel Authorization) and a VISA are both procedures required for entry into the United States, but they are different in their nature and purpose.
- ESTA: Intended for short-term stays of up to 90 days, available only to citizens of Visa Waiver Program (VWP) countries, and applied for online.
- VISA: Comes in various types depending on the purpose and length of stay (study, employment, long-term residence, etc.), available to citizens of all countries, and requires application and review through a U.S. embassy or consulate.
In short, ESTA is a simpler and faster method of obtaining travel authorization, while a VISA is a more formal permit designed for longer or specific types of stays.