Perhaps you should read the original post about Room Lighting to get the overall explanation for what it does and how it works.
"Activate" is used instead of "Turn On" because sometimes to activate the automation means to turn something off instead of on. Turn Off means what it says. How the automation is activated is defined by Means to Activate -- AND it can be done manually with the Activate button in the UI. Similarly, how the automation turns its devices off is defined by Means to Turn Off, with a UI button to do it manually.
The Device table provides more nuance to this, by allowing Activation to turn a device off, or specify exactly what should happen when the automation is activated. It also allows for some devices to not be affected by Activation at all, or affected by Turn Off at all (the Act and Off columns under Device Control). Here is an example of that:
Notice that Master is not touched by Activation. This is because it is handled outside of this automation. Notice the detail Activation setting for the two lamps, causing them to be set to color temperature mode with a specific CT and level.
The automation can omit turning some devices on upon activation, as shown above, It can also omit turning off some devices when Turn Off happens. Also, you should pay attention to the defaults that are set when you first set a Room Lights up. Those defaults are for the most common usage, where lights are turned on by Activation, and turned off by Turn Off.
