Bluetooth Low Energy (BLE) or Bluetooth Smart, is the low power- version of Bluetooth that was developed for the Internet of Things (IoT) and was introduced as part of the Bluetooth 4.0 core specification. BLE was originally developed by Nokia as an in-house project called 'Wibree' and soon after was adopted by the Bluetooth SIG. Bluetooth LE uses a 2.4 GHz unlicensed radio band to interconnect nearby devices. It provides a data rate of up to 1 Mbps while consuming just 0.01 to 0.5 watts.
In comparison to classic Bluetooth, BLE remains in sleep mode constantly except for when a connection is initiated. The actual connection times are only a few milli seconds, unlike Bluetooth which would take ~100mS. The reason the connections are so short, is that the data rates are so high at 1 Mb/s.
Bluetooth LE has been developed as a low power, low cost technology for infrequent short-range wireless data communication between devices, powered by nothing more than a dime-sized battery. Devices operating on Bluetooth Low Energy can operate for 5 years or even longer.