g|------------------1--2--4---|
d|------1--2--4--2------------|
a|---2------------------------|
e|----------------------------|
basically
each number is the fret you finger and you read(play) left to right
each letter denotes a string
e would be the closest to your face
then a d g
g being the farthest away
the key is though, tabs do not give time signatures and note length
so the only way a tab is really useful is if you know the actual song and can judge the timing
as far as learning actual reading of musical notes and key signatures
http://datadragon.com/education/reading/