For example, say I ask my media buying agency to buy me 300 rating points. They'd then go out and purchase time on shows where the total rating points of all those shows equals 100 (or partials thereof). Say "The Chelsea Handler Show" (love that woman) lands 20 ratings points that day/week/timeframe, her show would count as 20 grips (GRP's). Once you have your 100, you divide that into your total expenditure to get your CPP.

It doesn't always have to be television, but this is the easiest one to get at first. You could also look at CPP as cost per percentage point of the population you're trying to reach. For example, if you want 50% of all Adholers to see your message, you'd pay Marc (your media buying guy) to get you some space that 50% of Adholers would see. If Marc sold you a banner ad for $1000 that 50 percent of the adholers would see (50 GRP's), your CPP for that buy would be $20. Note, that's not CPA (cost per acquisition)... this is a percentage-based thing. 1% of 1000 people is 10 people. Let's say there were 1000 Adholers, your CPA for the same media buy would have been $2.