Play Bmaj9 one string at a time and you hear B, D#, F#, A# and C#. B is the root, D# the major third, F# the fifth, A# the major seventh and C# the ninth. Said aloud, its notes are B, D sharp, F sharp, A sharp and C sharp.
From the low string to the high one you hear B, D#, A# and C#. F#, the fifth, does not sound in this fingering. The lowest note is B on string 5 and the highest is C# on string 2.
Bmaj9 is a closed shape with no open strings. Move it to another fret and the chord changes, but the fingering stays. Strings 6 and 1 are not played. Everything fits between frets 1 and 3. The second shape on this page starts at fret 6.
From Bmaj9 to B9 only two strings change, 3 and 1. Bmaj9 holds the whole F# chord inside it, F#, A# and C#. Going to F#, two positions stay the same.
Bmaj9 shows up in four keys. In B major it is the Imaj9, in F# major the IVmaj9 and in D# minor the VImaj9. The rest appear in the key list.