Coins can be used to buy either their premium subscription (no ads and a few other things) or can be used to "award" posts/comments. You can select which award you want to give, there are multiple that are by reddit and there are awards that are subreddit specific. An award can also give the awardee some coins (e.g. you pay 200 coins and the awardee gets 100).
Like I think Reddit of ~2015 was a relatively sustainable lifestyle business, but the traffic numbers were way higher than that so there's the big push to turn it into another facebook/twitter.
That's a massive risk for their business. My guess is that they are going to get rid of the nsfw subreddits like tumblr did.
Maybe it's one of those whale markets like with in-app purchases, where <2% of the users are responsible for >80% of income.
That said, Reddit has also been giving out free awards that users can hand out, probably to try and get them hooked into the award system.
Huh, I haven't seen that. Do you have any examples? Everything I've seen seems to indicate that most people are at least vaguely entertained by awards, while acknowledging that they're pretty frivolous.
But yeah, I would definitely expect it would be a whale market.