Gsus2sus4 is G, A, C and D. It leaves out the 3rd and includes both the and .
Without a or , Gsus2sus4 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 Gsus2/4 or G suspended 2nd and 4th.

An open string adds a note without a finger: a tension on top or a pedal below. These belong to their key and cannot be moved up the neck.
In which keys. Every note of Gsus2sus4 belongs to C major (the V), D minor (the iv), E minor (the ♭III), F major (the ii), G major (the I), G minor (the i), A minor (the ♭VII) and Bb major (the vi).
Contains Gsus2sus4 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 Gsus2sus4 and adds minor third, flat thirteenth and flat seventh.
Contains Gsus2sus4 and adds minor third, sixth and flat seventh.
Contains Gsus2sus4 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.