sounds stupid but...

Each line of the tab represents the 6 strings of the guitar.  The top line of the tab represents the high E string, the second line represents the B string, etc. down to the low E string, which is the botton line of the tab.

The numbers in the tab show you which frets to finger for each string.  That's the basics.

There's a better description and some examples on this website:  <a href="http://guitar.about.com/library/blguitarlessonarchive.htm" target="_blank">http://guitar.about.com/library/blguitarlessonarchive.htm</a>

Hope that helps...

Trey