The A chord (major): notes A C# E, degrees 1 – 3 – 5. Guitar shapes: 542225, x02220, 577655, x-x-7-9-10-9.
A chord is the root plus degrees above it, most often stacked in thirds. Major and minor differ only in the lower third: a major third (M3) sounds bright, a minor third (m3) sounds sad. Pick a chord and a root to see its degrees and intervals, and its shapes.
m — minor, M — major, P — perfect, A — augmented interval; the number is the degree count. m3 is 3 semitones, M3 is 4, P5 is 7
A Am A5 A7 Am7 Amaj7 Asus2 Asus4 Aadd9 A6 Am6 A9 Adim Adim7 Am7♭5 Aaug