Tor is free software and an open network that helps you defend against a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security known as traffic analysis.
Tor protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world: it prevents somebody watching yourInternet connection from learning what sites you visit, and it prevents the sites you visit from learning your physical location. Tor works with many of your existing applications, including web browsers, instant messaging clients, remote login, and other applications based on the TCP protocol.
Hundreds of thousands of people around the world use Tor for a wide variety of reasons: journalists and bloggers, human rights workers, law enforcement officers, soldiers, corporations, citizens of repressive regimes, and just ordinary citizens. See the Who Uses Tor? page for examples of typical Tor users. See the overview page for a more detailed explanation of what Tor does, and why this diversity of users is important.
Tor doesn't magically encrypt all of your Internet activities, though. You should understand what Tor does and does not do for you.
Tor's security improves as its user base grows and as more people volunteer to run relays. (It isn't nearly as hard to set up as you might think, and can significantly enhance your own security.) If running a relay isn't for you, we need help with many other aspects of the project, and we need funds to continue making the Tor network faster and easier to use while maintaining good security.