Indicator formula structure

[Greg Haworth <GregHaworth@xxxxxxxxxxxxxxxxxx>]

Newbie Question

I just started playing around with MS, so please excuse what will seem like 
a "stupid" question.

I don't quite grasp the structure of the formulas.  I can't seem to find it 
in the manuals,  is there some kind soul out here that can direct me in the 
right direction?  I am specifically stumped trying to create a specific 
period MACD.  I tried modifying the canned DEMA MACD formula.

Here is where the structure eludes me.  I understand short, long, and 
signal periods (i think! short MA, Long MA, and averaging period) but why 
are there three terms in the brackets instead of just one??

I would take any guidance that can be offered -- i am really just a little 
overwhelmed.

regards/greg