Let's start and bring live into it by highlighting some of the words using the italic or bold or both styles. But there are different HTML commands to do this. You can use "strong" for the bold type and "emphasize" for italic. (See the source code for the actual commands.)
Other than those not effecting the flow of the text are the <H1> commands. "H" means "header" and defines a certain format (size, thickness and spacing) for the words in between <H1> and </H1>. Here is what it looks like.
And: The size of the headers may vary among different web browsers and on different computers. For instance there is no difference between the <H1> and the <H2> style in Netscape2.0b5 while there is in version 1.1. You may want to keep this in mind while creating your own page.
Relative to the actual default font you can also increase or decrease the font size.
This is basically looking like this ... and seems to be dependend on the browser and the computer too.
Ok. How about different background pictures or colored text now?