Pentatonic scale is a five note blues scale. It's also used a lot in rock and metal music. Some use it more than others, however every guitarist plays some pentatonic licks now and then.
Figure 1 is an illustration of all minor pentatonic positions on guitar fingerboard. 1st position is in the key of A.
Fig. 1 A minor pentatonic scale positions on guitar fingerboardA C D E G - minor pentatonic (1st position)
C D E G A - 2nd position (major pentatonic)
D E G A C - 3rd position
E G A C D - 4th position
G A C D E - 5th position
Figure 2 illustrates pentatonics and diatonic modes.
Fig. 2 A minor pentatonic scale positions and diatonic modes on guitar fingerboard
Think of minor pentatonic scale as a dorian scale without II and VI:A B C D E F# G - A dorian
A _ C D E __ G - A minor pentatonic
You will also find minor pentatonic scale in other two minor diatonic modes:B C D E F# G A - phrygian mode
B _ D E F# _ A - minor pentatonic over phrygian mode
E F# G A B C D - aeolian mode
E __ G A B _ D - minor pentatonic over aeolian mode
Figure 3 illustrates how minor pentatonic scale fits into different diatonic scales.
Fig. 3 Minor pentatonic scale in three minor diatonic scales
Think of major pentatonic scale as of lydian mode without IV and VII:C D E F# G A B - C lydian mode
C D E __ G A _ - C major pentatonic
You will also find major pentatonic scale in other two major diatonic modes:B C D E F# G A - D mixolydian
B _ D E F# _ A - D major pentatonic
E F# G A B C D - G ionian
E __ G A B _ D - G major pentatonic
Figure 4 illustrates how major pentatonic scale fits into different diatonic scales.
Fig. 4 Major pentatonic scale in three major diatonic scales