Target Rating Point

Television rating point for calculation purposes is a device is attached to the TV set in a few thousand viewers' houses for judging purpose. These numbers are treated as a sample from the overall TV owners in different geographical and demographic sectors.It records the time and the programme that a viewer watches on a particular day. Then, the average is taken for a 30-day period, which gives the viewership status for a particular channel.

Television rating points quantify the gross rated points achieved by an advertisement or campaign among targeted individuals within a larger population.

For example, if an advertisement appears more than once, the entire gross audience also, the TRP figure is the sum of each individual GRP, multiplied by the estimated target audience in the gross audiences. The TRP and GRP metrics are both critical components for determining the marketing effectiveness of a particular advertisement. Outside of television, TRPs are calculated using the denominator as the total target audience, and the numerator as the total impressions delivered to this audience x 100. (As in 1,000,000 impressions among the target audience / 10,000,000 people in total in the target audience x 100 = 10 TRPs). TRPs are often added up by week, and presented in a flowchart so a marketer can see the amount of impressions delivered to the target audience from each media channel.

...
Wikipedia