802.15.4 vs ZigBee vs XBee

IEEE 802.15.4 specifies the lower levels (physical and MAC or levels 1 and 2 of the OSI model) for a personal area network.

ZigBee is a collection of protocols built on IEEE 802.15.4. The ZigBee Alliance controls the protocols.

The XBee module is an implementation of 802.15.4/ZigBee by Digi.

General XBee stuff

Getting XBee to talk