Why are there chord letters above my Piano sheet music?

Guitar chords and piano chords are the same. You can just play chords instead of the notes but I play the chord and the notes. I would really need to see the music to explain it to you, but sometimes I play more notes than what the sheet music shows. If it has only melody note, I sometimes play 4 notes, the melody note plus the note an octave higher, then I add in-between notes that would be part of the chord.