Dave.

It’s BLE - Bluetooth Low Energy.

Basically devices with BLE can listen for a wake-up command and turn on, similar to the “magic packet” of wake on Ethernet.

Super convenient for “find my device” applications, also nice to be able to connect and activate the device without having to press a power button like a peasant.

It also means that most devices with BLE end up flat within a month. I had a speaker with BLE and had to deliberately download a much older version of the Android partner app to turn it off, as they dropped the option to do so in later versions for “convenience”. With BLE on it would be flat in about 6 weeks regardless of whether I’d used it or not , which really ruined ad-hoc usage for me.