Try looking at http://www.w3schools.com/ for HTML (can't be bothered explaining)
Also as for iFrames....
Just insert the following into the body of the document for example -
<iframe src="iframes/index.php" frameborder="0" height="100%" width="100%" name="master" ></iframe></td>
The
frameborder="0" is just to determine whether or how thick the border on the iFrame should be e.g. "0" means no border.
The
<iframe src="iframes/index.php" directs the iframe to show the file "index.php" stored in the directory "/iframes/" in the iframe.
Also
name="master" means that the iframe is refered to as "master" you can change this name but you MUST give the iframe a name if you plan to use links to connect to change the iframe for example...
<a href="iframes/index.php" target="master">Home</a>
That would set the text "Home" to lead to the link "iframes/index.php" but the new page would display in the iframe (if it is named "master").
I don't know if that helped but that was a very quick explanation for you.. :)