guitar chord
C♯m7♭5
A diminished triad with a minor seventh rather than a diminished one — half diminished, and not the same chord as dim7.
Written the other way round it is D♭m7♭5 — the same twelve keys on a piano, a different piece of notation.
Every fingering that fits a hand
x45000
easy
x42000
easy
x42003
easy
x4200x
easy
x45400
moderate · barre
What is true of it
C♯m7♭5 is C♯, E, G and B — 1, b3, b5 and b7 counted from C♯.
These are also the notes of Em6/C♯. Which name is right depends on what is underneath and what came before — the notes alone do not decide.
The easiest of the 5 fingerings below is x45000: 2 fingers, held at the 4th fret.
None of them uses an open string, so this chord moves up the neck unchanged — the same shape 1 fret higher is the chord a semitone above.
1 of the 5 need a barre.
1 string stays silent.
Where its notes are on the neck
The brass dots are C♯, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
C♯m7♭5/E
045000
C♯m7♭5/G
342000
C♯m7♭5/B
x22020
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.