Csus2sus4 is C, D, F and G. It leaves out the 3rd and includes both the and .
Without a or , Csus2sus4 is neither major nor minor. In jazz, sus chords can stand without resolving.
To hear what the adds, start with .
The 2nd drops two frets to a repeated root. The root, 4th, and 5th stay put.
Also written Csus2/4 or C suspended 2nd and 4th.

Drop the third voice from the top an octave instead. The wider gap skips a string, so the muted string is part of the shape.
That result, 3–R–5–7, is the shape usually meant by drop 3. Named by its bass note, as the inversions are here, it is the 1st inversion.
More familiar jazz shapes are drop 3 than drop 2.
In which keys. Every note of Csus2sus4 belongs to C major (the I), C minor (the i), D minor (the ♭VII), Eb major (the vi), F major (the V), G minor (the iv), A minor (the ♭III) and Bb major (the ii).
Contains Csus2sus4 and adds major third, sixth and major seventh.
Adds major third, sixth and flat seventh. The flat seventh pushes the sound toward a dominant chord.
Contains Csus2sus4 and adds minor third, flat thirteenth and flat seventh.
Contains Csus2sus4 and adds minor third, sixth and flat seventh.
Contains Csus2sus4 and adds minor third, flat thirteenth and major seventh.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.