BTLE is short for Bluetooth low energy, Bluetooth LE, or BLE, marketed as Bluetooth Smart, which is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group aimed at novel applications in the healthcare, fitness, security, and home entertainment industries.

Bluetooth low energy, Bluetooth LE, or BLE, marketed as Bluetooth Smart, is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group aimed at novel applications in the healthcare, fitness, security, and home entertainment industries.[1] Compared to "Classic" Bluetooth, BLE is intended to provide considerably reduced power consumption and cost while maintaining a similar communication range.

Bluetooth LE was originally introduced under the name Wibree by Nokia in 2006.[2] It was merged into the main Bluetooth standard in 2010 with the adoption of the Bluetooth Core Specification Version 4.0.

Mobile operating systems including iOS, Android, Windows Phone and BlackBerry, as well as OS X and Windows 8, natively support Bluetooth low energy. The Bluetooth SIG predicts more than 90 percent of Bluetooth-enabled smartphones will support the low energy standard by 2018.[3]

Check out its wiki-page for more details.