Well there are plent of tutorials all over the web about this subject, and probably even on this website. I'll give you the most lucid explanation that I can.

The skinniest string, the e, is on the top line. Then its goes down from b, g, d, a, low e.

e-------
b-------
g-----
d------
a------
e-----


The number on the line represent what fret you place your finger on. The fret is the space between the little line thingies on the neck of your guitar.

Hope I helped a little.