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