Tor, short for The Onion Router, is a free, open-source overlay network designed to enable anonymous communication and protect user privacy by masking IP addresses and browsing activity. Originally developed by the U.S. Naval Research Laboratory in the mid-1990s for intelligence communications, it is now maintained by the non-profit The Tor Project and relies on a global system of over 7,000 volunteer-operated relays.

The network functions through onion routing, a technique that encrypts data in multiple layers (resembling an onion) and routes it through three random nodes: an entry node (which knows the user but not the destination), a middle relay (which knows neither), and an exit node (which knows the destination but not the user). This process ensures that no single point in the network can trace the traffic back to its source, making it difficult for ISPs, governments, and malicious actors to monitor or censor internet usage.

While primarily used by journalists, whistleblowers, and activists in restrictive regimes to bypass censorship and protect sources, Tor is also accessible to the general public for enhanced privacy. However, its anonymity features have led to its association with the dark web, where it is used for both legitimate privacy preservation and illicit activities, resulting in a mixed reputation among law enforcement and security agencies. 

https://www.torproject.org/