Hey man! No problem
The reason for setting a key for the emitter at a high value (or any value other than zero for that matter), THEN, one or more frames later, keying it back to zero is very simple:
(my physics will be wrong here, but the idea is the same)
Think of a particle emitter like the light bulb in your dorm room.
Your light bulb is a particle emitter just WAITING to emit particles of light in all directions.
Your room, and the earth it resides in, has a default gravity value.
(In our case, we must ADD gravity to the scene, but that is easy.)
Anyhoo, you enter your dorm room, and you flip your light switch so the light turns on.
What happens? Light emits in all directions REALLY freakin fast
Now, what if you could control every aspect of the light that gets emitted from your dormroom lightbulb?
(amount, color, intensity, speed, direction, etc.)
In Maya you can
For example, say you just want to flip the switch and you want the light to only emit for a fraction of a second, BUT, still keeping the same intensity, color, amount, etc.
Well, thats what the 2-keyframe keying example above does.
You key the emitter so the lightbulb shoots a small burst of high intensity light very fast, then key it so it stops emitting, then you get to play around with the light that got shot out
Another way of looking at it is like turning the water faucet wide open, then shutting it off really quick.
The water that got shot out is still alive and swirling down the drain, but in our case, we caught it in a cup so we can use it for other purposes
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS