title: GitHub - jobs : what is : use actions/checkout
body: <p>I saw a lot of uses of :</p>
  <pre><code>jobs:
    myjob:
      steps:
        - name: checkout
          uses: &quot;actions/checkout@something&quot;
        - ...
  </code></pre>
  <p>But i can not find what is the purpose of the line :</p>
  <pre><code>uses : &quot;actions/checkout@something&quot;
  </code></pre>
  <p>Is it similar to this ?</p>
  <pre><code> run: git checkout something   
  </code></pre>