G/B Piano Chord
G/B is a G Major chord played over a B bass note. Because B is the 3rd of G Major, G/B is simply G Major in 1st inversion — the same notes, with the 3rd moved to the bottom.
The dark key is the bass note (B); the coloured keys are the G Major chord tones.
Notes in G/B
Low to high: B (bass) , then G – B – D.
How to play G/B
Play the bass note B low in your left hand, and the G Major chord (G – B – D) in your right. Because it's an inversion, the bass is already one of the chord tones — you're just voicing G Major with its 3rd on the bottom.