Guitar Theory Includes Scales, Chords, Progressions and More.

Guitar Chords
Consider your favorite song. It probably has guitar chords in it. Where do the chords come from? How are they built? What is the chord progression, that is, what are all the chords used, how are the chords combined and in what order? Why can the chords be combined in this manner?

Guitar Scales
Does your favorite song include a melody, guitar riff, lead guitar solo or bass line? Parts like these are derived from guitar scales. How are scales made? How are scales played on the fretboard? Which guitar scale does your song use? Why does the scale work over the chords and chord progression?

Guitar Keys and Chord Progressions
Do you think these questions are relevant? If you had to learn a song would it help you to understand how it was put together? How would knowing a song's key, chord progression and scales used effect how quickly you learned it? Would having a complete grasp of a song's inter-workings help you remember it better? Have you ever tried composing your own guitar music? When you know exactly how scales, chords and progressions are combined to make music, what will you do with this newfound knowledge?

Guitar Theory
As you can see, there are many benefits to learning the details of music and how they specifically apply to the guitar fretboard. Aside from being interesting, guitar theory can really open up your playing and greatly impact your rate of development. You'll pick up on new songs faster, retain more of what you learn, jam, improvise and compose your own music.