Quite a specific resource, I have already discussed it in other threads. The basic idea is to provide easy access to addon config data within a spreadsheet to allow scripters to make custom variables that take into account several of the variables already present.
In other words, if you want to make a 'demoralisation-from-sniper-fire' script, you could write a formula such as D = Hit Damage x range - audible fire * visible fire, or whatever, ad-hoc example but just to explain. You would then apply this formula to every weapon in the database (which I will expand) and the values returned would then be used in a script. It is also a time saving resource, I have put in the hours so you dont have to, as well as a fairly interesting weapons comparison chart that allows you to size up addons against each other. I have given a couple of examples of '3rd party variables' to show you what can be don but, to be honest, i'm sure other people will come up with much better examples. I originally designed it for use with Spooners money and shop scripts, as I needed a way to fairly price all the weapons - I use a large number of weapon packs.
ArmA Armaments spreadsheet by Callaghan