The D flat minor seventh chord is a 4-note chord consisting of the notes Db, Fb, Ab and Cb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Dbm7.
Chords that are a superset of Dbm7. The chords include more notes but always Db, Fb, Ab and Cb.
Chords that are a subset of Dbm7. These contain less notes but all of them are included in Dbm7.
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 Dbm7 chord. Feel free to save or share the image as needed.