Everything that we've put 
in our webpages so far

has been either 
content displayed by the browser,

or tags to tell the browser 
how to display it.

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

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

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

an exclamation mark, 
two dashes,

and some text inside here,

and then two dashes 
and a closing angle-bracket.

We call this a comment.

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

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

That's the thing about programs:

they're not just 
for computers to look at,

they're also for 
other humans to look at.

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

Okay, what do we use comments for,

besides just saying "hello" 
to our fellow humans?

Well, we might use them for 
letting people know

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

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

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

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

a very well trusted source.

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

and say, "These lyrics were from here."

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

Do you notice something 
about these comments?

They are all green.

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

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

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

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

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

We just surround it with a comment.

♪ (humming) ♪

Now, the browser 
no longer sees that HTML,

because browsers ignore 
everything in comments,

and that part is gone from the page.

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

by removing those comments 
on both sides...

and now it's back!

Remember, comments are for humans.

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

Which is pretty much 
all of us now, right?