What is the use of comments in HTML?

Answer 1

They can sometimes help organize your source code. E.g.

<!--begin navigation menu-->

They also can help others figure out what's going on more quickly.

<!-- kluge to work around bug #567890 in Firefox v57.0.2 on Android -->

Answer 2

Adding comments as your write code is a good practice, because they provide clarification and understanding when you need to refer back to it, as well as for others who might need to read it.