The B flat suspended fourth chord is a 3-note chord consisting of the notes Bb, Eb and F.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Bbsus4.
Chords that are a superset of Bbsus4. The chords include more notes but always Bb, Eb and F.
Chords that are a subset of Bbsus4. These contain less notes but all of them are included in Bbsus4.
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 Bbsus4 chord. Feel free to save or share the image as needed.