According to the indictment, TOR is a circuit of encrypted connections through relays on the TOR network that can be downloaded on home computers. TOR allows websites and electronic mail communications to mask IP address information by spreading communications over a series of computers, or relays, located throughout the world.
TOR is described by itself as:
Tor 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, 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.
Of interest is the investigation issues presented in a federal investigation of this type. First reported on in Rolling Stone, TOR which was allegedly used to provide privacy for its users on the online drug market was operating "above the radar" but is designed to allow people to be on the internet without leaving trails like Hansel and Gretel. It will be interesting to see what develops...stay tuned.