All
programming languages (that I've used, anyway) have a way to insert
comments--text that isn't read by the
interperator or
compiler, used by the programmer to write notes, remind him or herself to do something, etc.
HTML (which is a
markup language, not a programming language, BTW) also has a way to do this for the same reasons.
Similar to how it's done in programming languages, you put whatever you don't want to be displayed in the browser inbetween this tag: <!-- -->
Example:
<HTML>
<Body>
This text is being displayed to the browser
<!-- This text isn't, because it's inside the comment tag -->
</Body>
</HTML>
Nothing inside the tag will be displayed to the screen. In some programming languages you open a comment (like // blah blah blah in Java) and not terminate it, and it will automatically terminate at the end of the line. It's not like that in HTML, the comment only terminates with the -->.
Example:
<HTML>
<Body>
This text is being displayed to the browser
<!-- This text isn't
Neither is this, even though it's on a new line. -->
</Body>
</HTML>