How does category wise product ranking work in e-commerce websites?

I am learning about how ranking algorithms work on various websites. I found these resources -

Hackernews's Ranking Algorithm - https://medium.com/hacking-and-gonzo/how-hacker-news-ranking-algorithm-works-1d9b0cf2c08d

Reddit's Ranking Algorithm - https://medium.com/hacking-and-gonzo/how-reddit-ranking-algorithms-work-ef111e33d0d9

Reddit's comment Ranking Algorithm -https://redditblog.com/2009/10/15/reddits-new-comment-sorting-system

I am excited to know how category wise ranking algorithms work on e-commerce websites or websites like Quora/Pinterest/Stackoverflow.