It’s a place where users post links to sites and pages which they think the other users will find interesting. Those other users can then upvote the posts they think are interesting, and have discussions about the linked material.
Upvoting helps promote the best posts to the top of that day’s submissions, so that more people read it. Meanwhile, commenting and discussion is where the real value of the community comes in; often the discussion of a post is as insightful, if not more, than the original post.
Myself and another data scientist set up Machine Dreaming because we couldn’t find a decent online community that spans the areas we’re interested in. We hope Machine Dreaming will become this community!