title: Curly braces in string {0}
body: <p>I often see curly braces in a string usually containing a number, such as:</p>
  
  <pre><code>string something = "I have {0} cats";
  </code></pre>
  
  <p>Whilst I can work out what this means, I can say I've never read any documentation relating to its useage.  The c# string documentation seems to be void of any information relating to these.  Can anyone point me in the right direction?</p>