Bluetooth enables short-range wireless communication between devices.
Bluetooth is a wireless communication standard which uses ultra-high frequency (UHF) radio waves. Line-of-sight between the devices is not required, although it is only intended for exchanging data over fairly short distances, such as between a mobile phone and a headset.
Built-in Bluetooth support is available on the official Arduino BT board, and in various Arduino compatible development boards from third party manufacturers. Alternatively, Bluetooth support can be added to other Arduino boards through the use of a shield or generic components.
This tag should be used for questions about using Bluetooth with Arduino.