An Electronic Travel Authorization (eTA) is an entry requirement for visa-exempt foreign nationals traveling to a country, usually by air. It allows the destination or transit country to screen travelers before they arrive, increasing visibility and security. Here are some key points about eTA based on the search results:

• An eTA is electronically linked to a travelers passport and is valid for up to five years or until the passport expires, whichever comes first.
• Most travelers need a visa or an eTA to fly to, or transit through, a Canadian airport.
• The ESTA (Electronic System for Travel Authorization) is an automated system that determines the eligibility of visitors to travel to the United States under the Visa Waiver Program (VWP) .
• Authorization via ESTA does not determine whether a traveler is admissible to the United States. U.S. Customs and Border Protection officers determine admissibility upon travelers’ arrival.
• An e-Passport is required to use the VWP. An e-Passport is an enhanced secure passport with an embedded electronic chip.
• An ETA will soon be a requirement for people who do not have a visa and are traveling to the UK.

To apply for an eTA, travelers can visit the official website of the country they are traveling to, such as the Government of Canadas website. The application process is usually done online and requires biographic information and answers to eligibility questions.