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