A .onion address is a type of web address used by the Tor network, a system of computers that use layers of encryption to make users anonymous and keep their data secure. .onion addresses are only accessible through the Tor browser, which is a specialized browser that provides access to the dark web. The .onion address is a 16-character alpha-semi-numeric string.

Using .onion addresses provides a much higher level of security and privacy than standard URLs, as the data is encrypted multiple times and routed through a series of computers so that it is virtually impossible to trace the origin of the data. This makes it ideal for activities that require a high degree of anonymity, such as online banking, online shopping, and accessing sensitive information.

The dark web is a collection of websites that can only be accessed through the Tor browser. While many of the sites on the dark web are illegal, there are also a number of legitimate sites that are hidden from search engines and other standard web browsers. As .onion addresses are only accessible through the Tor browser, they offer a much higher level of security and privacy than other web addresses.