Originally, Low Energy. Bluetooth LE removes all the different communication modes and introduces a single, packet network based approach for everything.

You may remember the switch from bluetooth connections being something you had to manually enable every time you wanted it, to devices just being connected all the time (without causing your battery to drop). That’s what LE enabled.

The switch to the single packet network approach obviously also simplified everything else you might want to transmit.

The audio specs are still from the pre-LE era with different modes for everything you might do (modem, fax, headset, headphones, HID, etc), and LE Audio introduces a new and clean way for that.

To expand on that, there is a pretty accessible free book covering LE Audio available here https://www.bluetooth.com/bluetooth-resources/le-audio-book/...

"Lite".

The Bluetooth 5 spec is over a thousand pages long.

The Lite Edition spec is "only" a few hundred, IIRC.