Bm chord inversions
Bm/D and Bm/F# are the first and second inversions of the B minor. This means that the bass tone is shifting from B to D or F sharp.
Try in chord progressions
F#m - Bm/D - D
Bm - Bm/F# - G
Theory of the Bm/D and Bm/F# chords
Both chords consist of the notes B, D, F#. The difference is that the order of notes shifts. D is the bass note in the first inversion is and F# the bass note in the second inversion.
Chord constructionBm x - B - F# - B - D - F#
Bm/D x - D - F# - B - D - x
Bm/F# F# - B - F# - B - D - F#
Guitar versions of the chord
Notes in chordBm B - D - F#
Bm/D D - F# - B
Bm/F# F# - B - D
Only the order of notes differs
When stumble upon these chord names, you can choose to ignore the alternate bass note and play the regular B minor. It will always sound ok, but it may lack some subtle additions to the sound. The third diagram, noted with "alt.", is an alternative shape if you prefer to not play a barre chord.