From [this question][1]: 
>"The "interesting" tab is visible on the home page of Stack Overflow, and it shows the questions using one of the tags you added in your favorite list, **and other questions you could find interesting**" 

So yes, it should predominantly show questions you're actually interested in, but will most likely also show the odd question related to tags you've somehow visited. 

  [1]: http://meta.stackoverflow.com/questions/98719/interesting-tab