The Tor software protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world: it prevents somebody watching your Internet connection from learning what sites you visit, it prevents the sites you visit from learning your physical location, and it lets you access sites which are blocked.
The Tor Browser Bundle lets you use Tor on Windows, Mac OS X, or Linux without needing to install any software. It can run off a USB flash drive, comes with a pre-configured web browser, and is self-contained. The Tor IM Browser Bundle additionally allows instant messaging and chat over Tor. If you would prefer to use your existing web browser, install Tor permanently, or if you don't use Windows, see the other ways to download Tor.
Orbot is an application that allows mobile phone users to access the web, instant messaging and email without being monitored or blocked by their mobile internet service provider. Orbot brings the features and functionality of Tor (read more below) to the Android mobile operating system.