Google doesn't sell people to advertisers. For one thing, that would be illegal. For another, they don't have a delivery infrastructure that would support it. And, finally, advertisers aren't interested in buying people, they are interested in buying advertising impressions (particularly, ones that are targeted so as to be more likely to produce sales.)
What Google does is use information it receives from users to sell targeted advertising impressions in services that the users use. The users are suppliers -- both of the information and the advertising opportunities -- rather than either "customers" or "products".
What Google does is use information it receives from users to sell targeted advertising impressions in services that the users use. The users are suppliers -- both of the information and the advertising opportunities -- rather than either "customers" or "products".