Whole step
A whole step (also called a tone) is a distance of two half steps, for example from C to D. On the keyboard it is two keys along, counting every key, black and white.
Start on C and count two keys to the right: the black key is one, D is two. C to D is a whole step. Now start on E: F is one, the black key is two. This whole step ends on a black key, F♯, because there is no black key between E and F. Count keys, not colours.
Most neighbouring white keys are a whole step apart: C–D, D–E, F–G, G–A, A–B. Only two pairs, E–F and B–C, are a half step apart. The major scale is built from both: whole, whole, half, whole, whole, whole, half.
In interval names a whole step is a major second. British books call it a tone, and the half step a semitone.
What it sounds like
A whole step sounds calmer than a half step; it is the ordinary step of a scale. “Happy Birthday” begins with one: “Hap-py” stays on one note, and “Birth-” is a whole step higher.
Where it is taught: the studio’s interactive textbook, chapter 5, “Half steps, whole steps and the black keys”.