title: .collapsed , [collapsed="true"]
body: <p>I am working on a project. And in one of the css files it quotes:</p>
  
  <pre><code>    .collapsed, [collapsed="true"] {
         display: none;
      }
  </code></pre>
  
  <p>My question here is what does "collapsed= true" mean? And how does this work?</p>