The two main left hand styles to learn are rhythm and lead.

The left hand finger designations are shown above. The thumb is mainly used to guide the left hand along the neck and rarely used to fret notes. However, some players  DO fret notes with their thumb, but that requires a big hand to stretch around the neck. Jimmy Hendrix had HUGE hands and used his thumb most of the time. This allowed him to create a very unique sound and style all his own.

Rhythm guitar

When playing rhythm guitar, the left hand is responsible for changing chords. The hardest part for the left hand is switching between chords quickly. This requires a lot of practice and can take quite some time to master. The  left hand rhythm guitar arsenal is a chord vocabulary.

Learn only the chords to the song that you are studying at the time. There are hundreds of chords and you could get distracted trying to learn too many chords at once. Take your time, it's well worth the effort. It only takes three chords to play hundreds of songs so don't sweat it!

Lead guitar

When playing lead guitar, the left hand is responsible for playing scales and applying different types of techniques. Just like rhythm guitar, learning all the lead techniques requires a lot of practice and can take some time to master.

Your left hand lead guitar arsenal is technique like hammer on's, pull off's, bends, etc... An exmaple of one of the hardest technique in playing lead guitar is bending the strings to the correct pitch. I have seen many players bend a note either sharp or flat. It can make you sound out of tune.

Pitch and direction

Whether you want to play rhythm or lead guitar, you will end up having to navigate the fretboard.by going up and down the strings and frets. Here is a short video showing the left hand finger numbers, the left hand position, moving up and down the fretboard and strings. These are the basic movements that the left hand makes and is a good preperation for playing guitar in any style.

The notes