A hidden service is a website or online resource that is accessible only through specialized anonymity networks such as Tor (The Onion Router). Unlike regular websites, hidden services are not indexed by standard search engines and cannot be accessed via typical web browsers or the surface web. Instead, they use unique, often randomized, addresses ending with extensions like '.onion'. These services are designed to conceal both the server's location and the user's identity, providing privacy and resistance to censorship or surveillance. Hidden services are used for various legitimate and illicit purposes, including secure communications, whistleblowing platforms, and black markets.