it's a form of protection for the front end of your car. think along the lines of the acryllic bonnet and headlamp protectors that are factory fitted. A car bra does a similar thing, but whilst also protecting the paint, grilles, driving lights etc. And i believe it is an easier alternative to the acryllic stuff.
I have one and i swear by it for highway driving. I have done one 500km odd trip without it since i moved out of home, and i nearly cried at the amount of chips that were on the bonnet after. I'd touched up the chips with paint not long before so i knew they were from that single trip.
Not much use in the city, but highway and country it protects from bug splatter, stones and rocks, road grime, anything that trucks or other cars can fling up at it.
Toddlez, is yours designed for your car with the kit and such, or for a standard commodore front?