The chromatic scale is the entire scale of note possible. There are 12 notes and each note is a half step apart.

C to C# is a half step.
E to F is a half step, there is no E# or Fb nor is there a B# or Cb.

12 half steps make up the chromatic scale.

Going from C to D is two half steps or referred to as a whole step.

C - C#/Cb – D – D#/Eb – E – F – F#/Gb – G – G#/Ab – A – A#/Bb – B – C

On the guitar each fret is a half step, every other fret is a whole step.

Enharmonic Tones

C# and Db are called enharmonic equivalent notes since they are the same note just written differently they are also referred to as enharmonics.