Playing Accidentals on the Piano
You know that the black keys on a piano are sharps and flats; for example, a B-flat is the black key to the left of (or lower than) a B, and an F-sharp is the black key to the right of (or higher than) an F.
When piano music calls for you to play a sharp or flat not indicated in the key signature, these accidentals are placed on the same lines or spaces as their natural notes but with little symbols to the left of the notes. So B-flat sits on the B line with a little flat symbol next to it, and F-sharp is written on the F line with a sharp sign next to it. The natural sign cancels the flat or sharp, returning the note to its natural state.