Watch the Three Note Groups Pt. 1 online guitar lesson by Brad Carlton from Guitar Lab: Speed, Precision & Endurance Vol. 2
A major second interval is a whole step, which is two frets, and a minor second interval is a half step, which is one fret. This lesson will examine a three note layout involving a major second followed by a minor second. This major second minor second group occurs between the 2, 3, 4 and the 6, 7, 8 of the parent major scale of whatever mode you're in.