There are many different types of guitar tab. The most basic form that is used on the internet and computers a lot is simple text based guitar tablature. But is also used a lot by guitar players who don't have the software to create guitar tab. And of course many guitar teachers use it to explain things quickly.
Basic text guitar tablature Lets suppose you would play three chords on your guitar and the guitar chords are written in guitar tablature notation. The basic guitar tabalature looks like this.
This guitar tab shows an E minor chord (Em) followed by two versions of a G major chord (G). The first G major guitar chord is the the classic G major open guitar chord, the second G guitar chord is used by more and more guitar players because of it's warmth and power.
Chord picking in guitar tab Now that you know what chords look like in guitar tab here is what a picked chord looks like in guitar tab.