XBee is a module produced by Digi International mainly use as a radio communication transceiver and receiver. It is mesh communication protocols that sits on top of IEEE 802.15.4 ZigBee standard. XBee supports peer-to-peer as well as point to multi-point network communications wirelessly with the speed of 250 kbits/s.
Most of the XBee modules in the market are utilised the 2.4 GHz bandwidth with various type of antennas. They are whip antenna, U. Fl. RF connector and in-build chip antenna.
2 types of XBee standards were designed, the XBee and XBee PRO. XBee is designed based on low cost and low power at 1 mW. XBee PRO module is the power-amplified version of XBee module with 100 mW power. XBee normally is used in conjuction with Arduino hardware, but a XBee Arduino Shield is needed.
If you want to learn more about how to integrate XBee module with Arduino, this is a really good book to start with, Building Wireless Sensor Networks: with ZigBee, XBee, Arduino, and Processing from O’Reilly.