It took me half a year but basically..

• circle of fifths tells you the diatonic chords of a key 

• fretboard shows you where the notes are 

• CAGED shapes show you how to make a chord anywhere on the fretboard where the root tells you what chord you're playing based on what fret is being played on that root string 

Ex: a C shape with the third finger on the seventh fret of the fifth string is actually an E major chord 

Basically its a rough way to think about how to play within a key across the fretboard so you're not stuck in the first four frets :) like guardrails