It's a bit opaque right now, but we rank up content from authors we know are real people that write online...working to make this clearer in the interface.

The feed is ordered primarily by the what you've specified as interests and the salience of authors. As we find new essays that score high "relevance" when compared to the topics you've selected, your feed will be updated with more recent content.

In our personal use, we use it as a hybrid between feed of our favorite topics and exploring (stumbling upon) new things. The "prompt your feed" aspect definitely adds some search engine-like capabilities, while still letting you surf through the things you don't know about.