This is a Bb augmented 7 chord. It can be written as Bb+7. You might also see it as Bb7+5 or Bb7#5. The “+” is sometimes replaced with “aug”. I personally prefer Bb+7.

The notes are Bb (root), D (3rd), Ab (dominant 7th), D (3rd an octave higher), F# (5th raised a half tone).

The triangle shape on the bottom 3 strings tells you it is a dominant 7th chord (it may be easier to visualize this by moving the chord 1 fret higher).

The D (the 3rd) is repeated on the 2nd string.

This leaves the F# on the first string. The 5th for a Bb major chord is an F (look at the circle of 5ths and you’ll see that F is immediately to the right of Bb, which means it’s a 5th above Bb). The note in the diagram is an F#, not an F. If the 5th of a chord is raised a half tone, it is called “augmented”.

Note that I called the raised 5th an F# rather than a Gb. It think this is more appropriate because it better indicates the 5th is raised a half tone.

Of course, this could also be called A#+7. But A# chords show up a lot less often than Bb chords.