Guitar lesson: Learn to use correct left hand fingerings

Left hand fingerings are numbers in the sheet music indicating which finger you are suggested to use when playing a specific note. Usually when playing the first pieces on the guitar on the first frets it can be a good idea for you to play the notes on the first fret with your index finger, notes on the second fret with your middle finger, notes on the third fret with your ringfinger and notes on the fourth fret with your pinkie.

What then are the left hand fingering advantages? Can't you play every melody with your left hand index finger and forget about all this fingering stuff? Well, of course you can play melodies with your index finger but your progress will be very limited beyond just playing easy melodies. You'll have to move your left hand as you change frets and, most importantly, when reading sheet music, you'll have to look at the guitar fretboard instead of looking at the sheet music which means that it will be hard to sight read music.