A font is the way your text looks. There are many different fonts. How many? I don't really know. There seem to be new ones popping up all the time.
Every program has a default font. That is the font that you see, unless you change it in some way. The Net is the same way. Unless you specify a font, your page will look just like everyone elses.
The basic code to add a font style to your text looks like this:
<font face="font name">Text here.</font>
One thing you have to remember when using a different font, on your Web page, is that the person viewing your page may not be able to access the font you want to use. Their computer may not have it and then they can't see it. To them your text will look like the default Web font.
Something you may want to consider doing is naming more than one font, just in case the person viewing your page can't see the font you chose. This is done by laying out your code like this:
<font face="ms sans serif, geneva, arial">Text here.</font>
Here is a listing of a few fonts:
Futura T Bold
MS Sans Serif
Times New Roman