title: What does the distance attribute in DMatches mean?
body: <p>I have a short question: When I do feature-matching in OpenCV, what does the <code>distance</code> attribute mean of <code>DMatches</code> in <code>MatOfMatches</code>?</p>
  
  <p>I know that I have to filter matches with bigger distance because they aren't as good as them with lower distance. But what is the meaning of this attribute? Is it a kind of deviation?</p>