The Electronic Travel Authority (eTA) explained

The Electronic Travel Authority is an electronic authorisation which is issued in PDF format and is not visibly attached to the related passport. This form of visa waiver will be generated online through the designated website and will be submitted to the applicant’s inbox via email.

By gathering and screening vital information on applicants before they leave their countries, which can be verified against security databases, this new facilitation measure aims to expand security and accelerate border clearance procedures.

Many countries around the world already have or are presently implementing comparable measures to strengthen their borders and simplify the visa application process. The United States requires travellers from many countries, including the UK, to apply for their Electronic System for Travel Authorisation (ESTA), which is also completed online and is valid for two years.

Australia’s Electronic Travel Authority grants affected travellers a stay of up to 90 days for tourism or business purposes.

Europe’s ETIAS (European Travel Information and Authorisation System) will roll out in 2021. Visitors travelling to the Schengen Area will need this travel authorisation prior to embarking on their trip. The EU Commission has confirmed that travellers who are United Kingdom citizens will need to complete the online ETIAS application form to visit Europe after Brexit.