It's a place where you can subscribe to sub-reddits, sorta like the boards section found on the zone bbs, if you're familiar with it. Under a sub-reddit, people write posts, where they ask questions, write about things they've found on the internet, whatever and others write comments in response to what they posted about.
From what I've seen so far, the browser version with NVDA works pretty well, just have to move quite a bit through the pages, as there can sometimes be a great deal on each page. There is also a pretty neat IOS APP too, if you're interested.
Take care.