I figured I'd have a go at explaining the system to people that don't understand. Thanks to everyone that theorised with me and Blank, and lots of credit to you for working out what the bar on the right does. XD
The system is a turnbased/realtime hybrid, similar to FF4 - 9, but with some more dynamic elements.
-The ATB fills up in real time, similar to the systems in FF4 - 9.
-You can input commands as soon as an Action is full, meaning you don't have to wait for your ATB to completely fill up.
-Your character doesn't use commands as soon as you select them. Instead, you store them in the Input Slots and then press triangle (Execute) to use them all at once.
-Using more than one command at a time will create a combo. Every combo has a unique animation, meaning "Attack-Attack-Fire" will look different to "Attack-Fire-Attack".
-Your ATB will not fill up when you a Executing commands.
That's what we know for sure. If you have any questions, feel free to ask.
These are just theories, so don't take them as facts-
-There is a dodge move, completely seperate from the commands.
-You are in full control of your character's movement during battle.
-You will have a leader during battles (represented by the yellow flag).
-There may be some kind of AI system to control allies.
-Getting hit by an enemies attack may cause your combo to end prematurely.
-The Cure command is grey, I'm guessing that's significant. It would be a serious balance issue if you could use Cure whenever an Action was filled. Maybe you can only use it once per battle?