Tor is just Tor
Tor – aka The Onion Router
Tor is just Tor. It doesn't stand for anything any more.
It is used by whistleblowers, journalists, activists, crooks and lowlifes. All connections leaving the Tor network go through these exit points, which will inevitably carry a lot of traffic that the Feds will be interested in.
In fact it is used by anybody who wants to. The Feds are interested in e-mail, phone calls, and basically any traffic. Tor is not unique in this regard. One can, like with anything that one doesn't know about, make assumptions about what actual traffic is going through Tor and how much of it is related to illegal activity. Mostly because of the nature of the Tor network, there is no data available on traffic content, though several authors with dubious intent have tried to paint the situation as being whatever their paranoid minds can imagine. They don't, however, have scientific credibility. The Tor network itself is neutral, and that in itself is something that does not sit well with the current government.