A visa is an official document that allows a person to enter, stay, or leave a country for a specific purpose, such as tourism, work, or study. It is usually stamped or attached to a person's passport and indicates the duration and conditions of their stay. Different countries have different visa requirements, and the application process can vary widely. There are several types of visas, including tourist visas, student visas, and work visas. Each type serves a specific purpose and may require different documentation. It is important for travelers to understand the visa regulations of their destination country to ensure compliance and avoid legal issues.