piano chord
F♯dim
F♯1A♭3C♭5
Two minor thirds stacked. The fifth is diminished, so it cannot be dropped without losing the chord.
Written the other way round it is G♭dim — the same twelve keys on a piano, a different piece of notation.
What is true of it
F♯dim is F♯, A and C — 1, b3 and b5 counted from F♯.