A comparative rater is software that gets quotes from several insurers at once for the same client, so that an insurance agent can compare them side by side. It is also called a rating tool or a multi-carrier rater. It usually sits inside an insurance agency management system.
Without it, an agent who works with six insurers must type the same client's details into six insurers' websites. Each website asks the same questions in a different order. A comparative rater asks the questions only once. It then sends the answers to each insurer's rating system. The rating system is the part of the insurer's insurance core system that calculates the premium, the price of the policy. The quotes come back within seconds and are shown in one table.
Say an agent in Texas is quoting car insurance for a family with two cars and three drivers, one of them a teenager. The agent enters the family's details once: the cars, the drivers, their driving records and the cover the family wants. Six insurers receive the details. Four of them return a yearly premium, from $2,140 to $3,380. Two of them decline, because the teenager had an accident last year. The agent explains the two best offers to the family. The family chooses one, and the agent binds the policy. Binding means confirming the cover with the insurer, so that the cover starts.
Each insurer prices a risk with its own rules. This is underwriting, and it is why the same family gets very different prices. A comparative rater does not change any insurer's price. It only collects the prices faster, and puts them in one place.
India has the same idea in a different form. An insurance comparison marketplace shows customers prices from many insurers on one page. The main difference is the user. A comparative rater is a tool for a licensed agent, who then advises the client. A marketplace is a website on which customers compare policies themselves. The page on insurance distribution explains both routes.