what is a gross rating point
In advertising, a Gross rating point (GRP) is a measure of the size of an advertising campaign by a specific medium or schedule. It does not measure the size of the audience reached. Rather, GRPs quantify impressions as a percentage of the target population, and this percentage may thus be greater than, or in fact much greater than, 100. Target rating points express the same concept, but with regard to a more narrowly defined target audience. GRPs are used predominantly as a measure of media with high potential exposures or impressions.