Answer 1

HTML stands for Hyper Text Markup Language. It's the code that is used to make web pages. In your browser you can choose the "View source" option and see what it looks like :)

Comments

HTMLs for the dimwitted. Thanks Pokemaster.

Answer 2

With my editing powers, I shall reveal an example of HTML from Ninja's question here...

<iframe width="560" height="315" src="http://www.youtube.com/embed/SDmbGrQqWog?rel=0" frameborder="0" allowfullscreen></iframe>

<font color="Green">

This kind of HTML was compatible with the Markdown feature, but PM removed it for some reason, which is to be revealed here. There were various codes you could use to change font colors and such, but they were removed.