Bluetooth is a short-range wireless communications protocol used for peripherals. Bluetooth host support is mostly found in mobile devices such as cell phones and tablets but also becoming more common in laptops. Bluetooth USB dongles are also common.
Bluetooth is an alternative to proprietary wireless protocols more commonly used for wireless peripherals. Although the protocol is encrypted, the encryption is very weak. The vulnerability for eavesdropping is reason for Bluetooth being banned in many security-conscious environments.
Bluetooth keyboards and mice typically use at higher levels the HID protocol borrowed from the USB standard. Because of the limited bandwidth of Bluetooth, only equivalent to low-speed USB is possible: Bluetooth keyboards are therefore in effect limited to 6-key rollover.
The wireless standard was developed at Swedish telecom company Ericsson, and the name refers to the historic Nordic king "Harald Bluetooth", which according to legend would have had bad dental hygiene. (The Norse languages did not have the word "black", using "blue" to mean the same thing.)