For issues with the "Bluetooth Low Energy" profile.
What is "Bluetooth Low Energy"?
Mobile devices can do more and more things today, and ship with more and more powerful hardware. One thing has a hard way to keep up with this: the mobile device's battery. Its capacity doesn't grow with the same speed. One way to cope with that is making new hardware less energy-hungry. For this, the Bluetooth 4.0 specification introduced a new feature: Bluetooth Low Energy. The Wikipedia article1 puts it like this:
Bluetooth low energy (BLE) is a feature of Bluetooth 4.0 wireless radio technology, aimed at new, principally low-power and low-latency, applications for wireless devices within a short range (up to 50 metres / 160 feet -see table below). This facilitates a wide range of applications and smaller form factor devices in the healthcare, fitness, security, and home entertainment industries.
When should I use this tag?
If your device already supports Bluetooth 4.0, announces BLE compatibility, and you are having issues with it, the bluetooth-le tag is the one you should use.