What Is Hilltop?
The Hilltop Algorithm was created by Krishna Bharat and George Mihăilă before Google hired them. It was an early way for Google to find the best websites to show in search results. It worked by:
Identifying "expert" websites that linked to lots of sites on a particular topic
Seeing what sites those expert sites linked to
Showing sites that got links from lots of expert sites higher in search results
So it used links from sites that were seen as "experts" to figure out which other sites were also authoritative and useful on a topic. This helped Google rank the most credible and recommended sites at the top of search results.