Here is a good beginner friendly introduction to the CAGED system for guitar players.
So what is the CAGED system and how can it help? Well as a beginner you typically learn to play chords in one position on the fretboard, the rest of the fretboard remains a mystery! The CAGED system helps you learn to play chords (and scales) across the fretboard.
Why is it called CAGED? It is called CAGED because it is based on the five open chord shapes C, A, G, E and D.
To give you an example of how CAGED works, think of the C chord, the root note C is on the 5th string (3rd fret). If you now start a barre at that note and play an A shape, you are now playing a C chord a bit higher up the fretboard. You can repeat this for the G shape, E shape and D shape, playing the C chord up the fretboard.