Found this on the Unreal forums.
Regarding the “magic numbers” - Im guessing this is a “beginner” tutorial and wont go too much in-depth about coding practices. At this point, theres no need to have those numbers as Parameters. Maybe they change it a future lesson.
Triggered - This fires every frame while “triggered”. If no new trigger is added, the default trigger is ‘down’. It will fire any time the keys value is not at its default. For single key presses this means “triggered” will fire every frame the key is held down. The mouseXY axis will fire every frame that mouse movement is detected. If you add a hold trigger, and set the hold time to 5 seconds, trigger will not fire until the key has been held down for 5 seconds, and then it will fire every frame until the key is released, or just once if “one shot” is enabled. I’d recommend getting a solid understanding of the enhanced input system before learning the various triggering methods.
Started - This will fire once when key is pressed no matter what. Even if you set the input value to trigger after the key is held for 5 seconds, this will still fire once when the held timer first starts. For the Mouse XY, this will fire once when the mouse starts to move and won’t fire again until a frame passes where mouse movement isn’t detected.
Ongoing - This will fire each frame that the key is pressed, but not yet triggered. If I have an action that triggers after the key is held for 5 seconds, ongoing will fire every frame during that 0 - 5 second period, and then stop when the action triggers or button is released. If the trigger is default type(down) I don’t think this does anything.
Cancelled - This will fire once if the condition for triggering was started but not completed. If I have an action that triggers after the key is held for 5 seconds and I hold the key for 3 seconds and release it before it reaches 5 seconds, cancelled will fire one time. If the trigger is default type(down) I don’t think this does anything.
Completed - Will fire one time if the action is completed. The default trigger will cause this to fire whenever the key is pressed down and released. If I have an action that triggers after the key is held for 5 seconds, this will fire one time after it is held for 5 seconds if the trigger is “one shot”. If the trigger is not one shot completed will fire when you release the key. For the mouseXY axis, this will fire whenever the mouse stops moving.