The "in between" notes in the chromatic scale can be described as either sharps or flats. Because of the way scales and chords are constructed, flats are used more often than sharps. Here once again is the C chromatic scale with scale degrees under the notes. The scale degrees written here relate to the natural notes and the flat notes. The sharps are enharmonic equivalents, which means they are the same pitch (e.g C# = Db and F# = Gb).
This melody in the key of G contains several accidentals. Play it slowly and notice how your left hand fingers move small but specific distances to form the sharp, flat and natural versions of notes.
Here is a piece which alternates between the key of E minor and its relative – G major – and also contains several accidentals. This one is quite challenging, so practice it slowly at first, and only increase the tempo when you can play it perfectly.