Half steps & whole steps

The half step (or semitone) is the smallest step on our standard twelve-tone keyboard: from any key to the very next key, black or white. On the keyboard, E→F and B→C are half steps because there is no black key between them.

A whole step (tone) is simply two half steps stacked — one key skipped between. C→D is a whole step; so is F→G. Almost every scale you will ever learn is just a specific recipe of whole and half steps.