Search engines go from link to link, it makes sense. But how do they find pages on autotrader, cars.com, ebay and other big websites if they dont really have links to them, you gotta do a manual search, choosing like 10 different options before you can actually find something. How do search engines find those pages? Do does website have some trick built into the website that whenever someone posts something, it automatically creates a link somewhere that points to that ad?
Because there are links to them from the homepage. Search engine crawlers follow *every* link, eventually finding every single page on a website that can possibly be clicked to form the homepage.