So that’s what third party cookies are. What this does is make it so that when you go to example.com and you get a Google cookie, that cookie is only associated with example.com, and your random.org Google cookie will be specific to that site.
A site will be able to use Google to track how you use their site, which is a fine and valid thing, but they or Google don’t get to see how you use a different site. (Google doesn’t actually share specifics, but they can see stuff like “behavior on one site led to sale on the other”)