GRP, or Gross Rating Points, is a metric used in advertising to measure the total impact of a campaign on a specific audience. It takes into account both the reach and frequency of an ad, providing a more comprehensive understanding of its effectiveness. GRP is calculated by multiplying the percentage of the target audience reached by the number of times they were exposed to the ad. This allows advertisers to gauge the overall impact of their message and make informed decisions about their marketing strategy. In short, GRP is a valuable tool for measuring the success of an advertising campaign and maximizing its impact on the intended audience.