It doesn't. For the ad platforms, this lets them optimize their ads for better performance when they know which user profiles converted. For advertisers, it's

It doesn't. For the ad platforms, this lets them optimize their ads for better performance when they know which user profiles converted. For advertisers, it's used for directional guidance on the platform, e.g. ad campaign A converts at 3x the rate of ad campaign B. The famous quote in the industry is "Half the money I spend on advertising is wasted; the trouble is I don't know which half." This method gives you a better idea of which money is wasted, at least compared to something like a TV or a print ad. It gets more complex when you're advertising on multiple channels. For instance, if you see an ad on FB, Google the product, then buy it, both will take credit for a conversion even though your business only had one sale. There are more scientific methods for modeling advertising results from multiple channels [1], that leverage control groups (say you run a Google ad in New York and a TV ad in California and monitor which market sees a bigger spike in sales). [1] https://en.wikipedia.org/wiki/Marketing_mix_modeling https://en.wikipedia.org/wiki/Marketing_mix_modeling