DSG, I think they he means "disabled" like the trigger is simply turned off.
Though there is an extra option in trigger editor to completly deactivate a trigger (marked with a red cross), then it would not even compile.
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Normaly disabled triggers, so ones you can turn on later again, won't be unregistered by the used event(s).
But that's probably not so important because onEvent, it won't fire the trigger's evaluation and execution part (so running the trigger), and so it's not really consuming resources.
It's good practice to turn triggers off that are needed only temporary.
And the bigger the code-body is and the more operations are done insde, the more effect it will have obviously.