This package is for doing fantastic things with your XBee device. You can, of course, already use it as a serial replacement, so you can run PPP and UUCP across it. XBee radios are low-cost, long-range, low-speed devices; with bitrates from 10Kbps to 250Kbps, they can reach many miles using simple antennas and low cost.
XBee devices are particularly interesting because of their self-healing mesh (DigiMesh) technology. They will auto-route traffic to the destination, via intermediate hops if necessary. They also support bitrates high enough for a TCP stack, with nearly the range of LoRA.