title: What do 3 dots/periods/ellipsis in a relay/graphql query mean?
body: <p>The <a href="https://facebook.github.io/relay/docs/graphql-object-identification.html#content" rel="noreferrer">relay docs</a> contain this fragment:</p>
  
  <pre><code>query RebelsRefetchQuery {
    node(id: "RmFjdGlvbjox") {
      id
      ... on Faction {
        name
      }
    }
  }
  </code></pre>
  
  <p>What does this <code>... on Faction</code> on syntax mean?</p>