And here's another guide on how to learn 'Stairway to Heaven' Intro in 20 Minutes.
Lines stand for guitar strings.
The top thin line signifies the first string.
The bottom thick line signifies the sixth string.
Numbers indicate which fret you should hold down the string.
So a line with a number on it indicates a string pressed on a certain fret.
0 means that it's an open string.
It's as simple as that.