piano chord
C♯sus4
C♯1F♯4G♯5
The third replaced by the fourth, which leans on the third it is standing in for.
Written the other way round it is D♭sus4 — the same twelve keys on a piano, a different piece of notation.
What is true of it
C♯sus4 is C♯, F♯ and G♯ — 1, 4 and 5 counted from C♯.
These are also the notes of F♯sus2/C♯ and G♭sus2/C♯. Which name is right depends on what is underneath and what came before — the notes alone do not decide.