The D flat diminished seventh chord is a 4-note chord consisting of the notes Db, Fb, Abb and Cbb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Dbdim7.
Interactive piano diagram for the D flat diminished seventh chord
Chords that are a subset of Dbdim7. These contain less notes but all of them are included in Dbdim7.