Bbsus2 is Bb, C and F — with the third replaced by the second.
It sounds open, and neither major nor minor. With no third it works over either quality, which is why strummed parts lean on it.
Suspended — it hangs until something moves.
Also written Bb2 or Bb suspended 2nd.

Voice by voice, Bbsus2 → . No voice moves by a semitone, and 2 notes are common to both chords. No voice has to move by a semitone, so this is a change of colour rather than a resolution.
| In Bbsus2 | Moves | In Bb |
|---|---|---|
| Bb, the root | stays where it is | Bb, the root |
| C, the second | falls a whole tone | Bb, the root |
| F, the fifth | stays where it is | F, the fifth |
In which keys. Every note of Bbsus2 belongs to C minor (the ♭VII), C# major (the vi), D minor (the ♭VI), Eb major (the V), F major (the IV), F minor (the iv), G minor (the ♭III), Ab major (the ii), Bb major (the I) and Bb minor (the i).
Every note of Bbsus2 is in Bb major pentatonic, Bb major, Bb natural minor, Bb dorian and Bb mixolydian.
Each of those is a page: the scale across the neck, and the chords it harmonises into — which is where Bbsus2 sits in it. Every scale.
Change one note of Bbsus2 and you have (the second becomes the major third), (the second becomes the minor third), (the second becomes the fourth), (add the fourth), (add the major third) or (add the minor third).
Bbsus2 is a suspended chord — root and fifth, with a second or fourth where the third would be — or nothing at all. Suspended and power chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.