It's quite simple really, each line of tab represents a string on your guitar.
The top line is your 'top' string (the thinnest one) and the bottom line is you bottom string (thickest one).
So it's like this:
e----------------------------- (high e)
B-----------------------------
G-----------------------------
D-----------------------------
A-----------------------------
E-----------------------------
Each number is just the fret number you play. So for instance:
e---0--------------------------
B---0--------------------------
G---1--------------------------
D---2--------------------------
A---2--------------------------
E---0--------------------------
Would be how you represent an E chord in tab.
Simple eh?