Barre chord
fret 1, A shapex13321
B♭m is the B♭ minor chord. Its notes are B♭, D♭ and F. It is the same chord as A♯m. The lowered third gives this triad its darker color.
x13321
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Numbers show frets from the low E string to the high e string; x means don't play that string.
B♭m is the ii chord in A♭ major, the iii chord in G♭ major and the vi chord in D♭ major. That makes it a natural fit in songs written in those keys.
Every B♭, D♭ and F on the first 12 frets. The filled dots are the root, B♭. Build your own shape from any nearby group.
Other B♭ chords
Other minor chords