The C sharp suspended second chord is a 3-note chord consisting of the notes C#, D# and G#.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as C#sus2.
Chords that are a superset of C#sus2. The chords include more notes but always C#, D# and G#.
Chords that are a subset of C#sus2. These contain less notes but all of them are included in C#sus2.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the C#sus2 chord. Feel free to save or share the image as needed.