The FedNet (short for Federal Hypercommunication Network) allows for real-time communications between people on different planets throughout known space. After the fall of the Earth Federation and the rise of the Holy Terran Empire, the name was officially changed to the Imperial Hypercommunication Network, although most people still refer to it as "FedNet" out of habit.
Calls and other data transmissions from planets, space stations, starships, etc. are sent to orbital communication satellites by conventional means, which then route the information to a specialized satellite that converts the data into a tachyon stream and sends it into hyperspace trough a tiny jump point that the satellite constantly keeps open. From there, that system's hyperspace navigation beacon picks to the tachyon stream and beams it through hyperspace to the navigational beacon in another star system. The data stream may need to be routed through several different beacons in the jumpgate network to reach its final destination, but because tachyons move faster than the speed of light, the transmission is effectively instantaneous, allowing for real time communication between planets thousands of light years apart. This way, it's possible for a businessman or hacker to place a phone call or tap a computer on the other side of known space.
The K'Nes and Jurvain maintain their own hypercommunication infrastructures which are compatible with humanity's. The K'Nes communications network is fairly open in an effort to promote and facilitate business and trade, but the Jurvain network is restricted and carefully monitored, as those xenophobic aliens are always suspicious of any contact with humanity.
Behind the ScenesEdit
In the TI Universe, the FedNet basically exists as a convenient bit of handwaving to allow players and writers to have real-time conversations between characters in different parts of space. Using tachyons for instantaneous interplanetary communication is a science fiction trope that's been around for decades. The alternative, which requires messages being carried by starship and taking days to reach thier destination, was deemed by the players to be too inconvenient, cumbersome, and annoying to deal with. The name and iconography of FedNet was borrowed from the Starship Troopers Movie.