Tab--

6 lines

The bottom line would represent your "thick, fat, E string" or 6th string. Next line above, the 5th so on and so on.

The numbers written on that line represent the fret you would use to play the note/tone.

When you have numbers written "on-top" of each other this would represent a chord , double stop or many note played at the same time.

You would just follow the numbers to learn a particular riff, chord progression etc. ince most internet tab does not have music notation it relies upon you to understand wher and when to play the notes.

Hope that helps.