Confuse on <!-- -->

Tell us what’s happening:
Describe your issue in detail here.

  **Your code so far**

<html>
<body>
  <h1>CatPhotoApp</h1>
  <h2>Cat Photos</h2>
  <!--TODO: Add link to cat photos.-->
  <p>Click here to view more cat photos.</p>
</body>
</html>
  **Your browser information:**

User Agent is: Mozilla/5.0 (X11; CrOS x86_64 14588.123.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.72 Safari/537.36

Challenge: Step 4

Link to the challenge:

Hey, @zhangsiya24
I assume you don’t understand what <!-- TODO: Add link to cat photos. --> means.
That is a comment. The browser ignores comments, but they are useful for humans. You can write notes, explanations, todos, etc. for your future self or for other people. In other languages comments look like this //elaborate description or this /* many words */ or this #abababababanana. In html they start with <!-- and end with -->.

Hope this helps.
Cheers