Scales
A scale can be defined as a series of notes, in alphabetical order, going from any given note to its octave and based upon some form of set pattern. The pattern upon which most scales are based involves a set sequence of tones and/or semitones. On the guitar, a tone is two frets and a semitone is one fret. As an example, the B note is a tone higher than A, (two frets), whereas the C note is only a semitone higher than B (one fret). Of the other natural notes in music, E and F are a semitone apart, and all the others are a tone apart.
Natural Notes
In music theory, a tone may be referred to as a step and a semitone as a half-step.
The main types of scales that you need to become familiar with are the chromatic, major, minor, minor pentatonic and blues scales.
