Toggle key
The Toggle key will execute the Toggle command.
This will turn on or off an executor. If an executor is active then you can deactivate it by pressing Toggle and then the executor. If it's not active then it will turn on when you use the command.
If you know what status you want the executor to have, then you can use the On and Off keys.
This is the default function for the executors without faders.
If you need this function on any executor key, then you can press 
and Label keys together (this will give you the Assign command), then press Toggle and then the desired executor key. You can also use the Change Functions of Executor Buttons Window.
Advanced Functionality
If you press and hold the key and then press the Toggle key then you get the Temp command.
This can be used to run an executor temporary. When you press the + Toggle and then press a key associated with an executor, then the executor will be active as long as you hold the key pressed.
When you press the executor key the actual Temp command is executed and when you release the key, then you execute a Temp Off. This will also turn off the executor if it was running before you did the "temp".
You can assign the Temp function to a key just like described above.