Most Reddit pages have a throwback aesthetic, with a few crudely designed graphics and a tangle of text: an original post, comments on the post, responses to the comments, responses to the responses.

To its devotees, Reddit feels proudly untamed, one of the last Internet giants to resist homogeneity.

A link aggregator? A microblogging platform? A social network? The only truly surprising entry, in fourth place, is Reddit, whose astronomical popularity seems at odds with the fact that many Americans have only vaguely heard of the site and have no real understanding of what it is. (Porn, somewhat hearteningly, doesn’t crack the top ten.) The rankings don’t reflect everything-the dark Web, the nouveau-riche recluses harvesting bitcoin-but, for the most part, people online go where you’d expect them to go. Which Web sites get the most traffic? According to the ranking service Alexa, the top three sites in the United States, as of this writing, are Google, YouTube, and Facebook. To hear more feature stories, download the Audm app for your iPhone.