The F eleventh chord is a 5-note chord consisting of the notes F, C, Eb, G and Bb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as F11.
Chords that are a superset of F11. The chords include more notes but always F, C, Eb, G and Bb.
Chords that are a subset of F11. These contain less notes but all of them are included in F11.
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 F11 chord. Feel free to save or share the image as needed.