sus2 and sus4 chords replace the 3rd in a triad.
They use the 2nd note of the scale or the 4th note of the scale rather
than the 3rd note.
Typical Major triad = 1, 3, 5 (or in C) C, E, G.
A sus2 Triad = 1, 2, 5 (or in C) C, D, G.
A sus4 triad = 1, 4, 5 (or in C) C, F, G.
Pt