It means Bluetooth Low Energy.
Bluetooth Low Energy (Bluetooth Low Energy, also known as Bluetooth LE, BLE, old trademark Bluetooth Smart), also known as low-power Bluetooth, is a personal area network technology designed and sold by the Bluetooth SIG. For emerging applications in healthcare, sports and fitness, beacons, security, home entertainment and other fields. Compared with classic Bluetooth, Bluetooth Low Energy aims to significantly reduce power consumption and cost while maintaining the same communication range.
Compatibility:
Bluetooth low energy is not backward compatible with the original Bluetooth protocol (hereinafter referred to as classic Bluetooth).
Bluetooth Low Energy uses the same 2.4GHz radio frequency as Bluetooth Classic, so dual-mode devices can share the same antenna. Bluetooth Low Energy uses a simpler modulation system.