C, C#, D, D#, E, F, F#, G, G#, A, A# and B.
'#' is a symbol used to denote the word 'sharp'. If you have noticed, a keyboard has white and black-colored keys. If you observe carefully, you will notice that the black keys are arranged in groups of twos and threes. The first black key in the group of two denotes the note C#.