12 Bar Blues is a pattern of chords which repeat every 12 bars. There are hundreds of well known songs based on this chord progression, i.e., they contain basically the same chords in the same order. 12 Bar Blues is commonly used in Rock music and is the basis of Blues music.
The following 12 Bar Blues is in the key of E major. When a song is said to be in the key of E major, it means that the most important chord (usually the first chord) is the E chord. This pattern of chords will probably sound familiar to you.
In bar 9, a new note B is introduced.
Play this note with the fourth finger of your left hand just behind the fourth fret of the 1st string.
The small numbers next to the notes in bar 9 indicate which left hand finger to use. Whenever different or unusual fingering is required, fingering numbers are used.