A key change sounds fancy but it's just the whole family moving house: same four jobs — Home, Away, the Question, sad cousin — new Home. For a beginner there's one magic tool, the capo. Clamp it on the 2nd fret and every open shape you know jumps up a whole step. Capo 2 with G shapes = the key of A, no new chords to learn. That's a real key change, done with a clamp.