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Everything that we've put 
in our webpages so far

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has been either 
content displayed by the browser,

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or tags to tell the browser 
how to display it.

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Sometimes though, we just want to put 
information in our webpages

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for other humans to read, 
and for the browser to ignore.

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To do that, we write 
an opening angle-bracket,

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an exclamation mark, 
two dashes,

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and some text inside here,

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and then two dashes 
and a closing angle-bracket.

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We call this a comment.

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And it's something that we do 
in all sorts of programming languages,

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because we often want to do things 
that are just for humans.

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That's the thing about programs: 


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they're not just 
for computers to look at,

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they're also for 
other humans to look at.

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Because we often work together 
on things and learn from each other.

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Okay, what do we use comments for,

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besides just saying "hello" 
to our fellow humans?

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Well, we might use them for 
letting people know

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where content came from, 
in case they want to update it.

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I'll say, "This paragraph is based on 
the Wikipedia article,"

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and I should probably 
give a link to that, too, but...

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And, "This paragraph is based on 
Pamela's personal opinion,"

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a very well trusted source.

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Then maybe we'd even, say, 
give a link inside the comments,

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and say, "These lyrics were from here."

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And that helps people know 
how I got the content of this page.

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Do you notice something 
about these comments?

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They are all green.

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That's because we're using a code editor 
with syntax highlighting,

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and it uses colors to help us 
see what's what,

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and comments are pretty much 
always colored green, by convention.

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We could also use comments to 
"comment out" parts of our HTML.

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Like if we want to experiment with
taking something away from our webpage.

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We just surround it with a comment.

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♪ (humming) ♪

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Now, the browser 
no longer sees that HTML,

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because browsers ignore 
everything in comments,

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and that part is gone from the page.

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If I decide that I actually liked it, 
I can comment it back in

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by removing those comments 
on both sides...

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and now it's back!

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Remember, comments are for humans.

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At least, the kind of humans that 
like to look at webpage code.

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Which is pretty much 
all of us now, right?