title: GeoDjango, difference between dwithin and distance_lt?
body: <p>Using geoDjango, what is the difference between </p>
  
  <pre><code>myObj.objects.filter(point__dwithin(...etc.))   
  </code></pre>
  
  <p>and </p>
  
  <pre><code>myObj.objects.filter(point__distance_lt(...etc.))  
  </code></pre>
  
  <p>?<br>
  Are they the same thing, or are they doing subtly different things?</p>