The G flat minor eleventh chord is a 6-note chord consisting of the notes Gb, Bbb, Db, Fb, Ab and Cb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Gbm11.
Chords that are a subset of Gbm11. These contain less notes but all of them are included in Gbm11.
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 Gbm11 chord. Feel free to save or share the image as needed.