New ask Hacker News story: Ask HN: What kinds of cookies are “required” for a website to function?

Ask HN: What kinds of cookies are “required” for a website to function?
4 by sriku | 3 comments on Hacker News.
... apart from login cookies. Many sites which don't require you to login ask for permission to store cookies "required for the site to function" and don't let you refuse them. What exactly do these cookies do? Would appreciate answers from folks who are site devs for any such websites.