When you click through to the New York Times, as the page is loading, there is an instantaneous algorithmic auction for the right to show you an ad impression. That auction takes about a tenth of a second. In that tenth of a second, the New York Times passes on all of your cookies to an online auctioneer called a supply-side platform. These auctioneers then send out a query to a whole bunch of bidding companies that exist to help advertisers run online ad campaigns. They'll say, essentially, "At 4:01 pm, from the following IP address in Cambridge, Massachusetts, somebody we think is female, twenty-five to thirty-five years old, is looking at an article about Trump."
