Whole Step and Half Step

Whole Step and Half Step

Whole step or full tone and half step or semi tone is the distance between the two notes.

 Semi Tone or Half  Step

 Semi tone or half step means distance from any note to the very next note, semi tone up means half note higher then the previous note and semi tone lower means half note low from the next note.

Full Tone or Whole step

 Full tone or whole step means two semi tone are put together. Full tone up means two semi tone higher than the previous note and full tone lower means two semi tone lower than the next note.

The only naturally half step or semi tone are between 

 E -F and B - C  

E - F and B - C is semi tone distance. Between these two pair of notes only have semi tone or half step distance, all other pair of notes are full tone or whole step distance.

Example 

C to C# is semi tone or half  step up and C# to C or Db to C is semi tone down. C to D is full tone 

or whole step higher and D to C is full tone or whole step down.

On guitar each fret distance are semi tone distance and two fret distance are full tone or whole step distance. First fret to second fret distance is semi tone or half step distance and first fret to third fret distance is full tone or whole step distance.

On piano each key whether it white or black is half step or semi tone apart from the next key.
The distance from the first white key to in between black key is semi tone or half step distance, and the distance from the first white key to second white key with a black key in between two white keys is full tone or whole step distance, only there are no black key between E-F and B-C.