a suspended2 also a sus2, basically if you know you major scales you should understand this,,,,,ok say you have the C major scale,,C D E F G A B

K if a major chord is based on the R,3,and 5 of the scale then a sus2 (or any kind of suspended) chord is just going to replace it with what number it has

so a sus2 is replacing the 3rd with the 2nd of the major scale, in the key of C, a major scale is C E G, now just replace the C with the D, now you have CDG, a sus2 chord,, im only 14