A full-featured ad blocker (uBlock Origin original, not the neutered Lite version that runs on Chrome now) will intercept requests at the network level and prevent your browser from requesting the advertisers' JavaScript code. Your browser not only won't show the ads, it won't run the code that was supposed to show them or even send a request to the advertisers' servers.
This blocks most existing tracking methods. The only thing you're not protected from is first-party tracking by the site you're actually visiting, which is impossible to fully protect against.
This blocks most existing tracking methods. The only thing you're not protected from is first-party tracking by the site you're actually visiting, which is impossible to fully protect against.