Remind me about the subtle differences in different kinds of waits

So a DELAY (even without cancel-ability) just backs up triggered actions where, in the example below, the DELAY would not stop a backlog of repeating this rule's actions? I thought the DELAY was how you prevented this when you do not want the actions repeated for a few minutes despite continued triggering.

--> first trigger occurrence

action A
action B
DELAY 5 min

---> second trigger occurrence


Addendum: Putting this here for future readers.