Pitch

Pitch describes the frequency of notes, where quicker vibrations are higher frequency or higher in pitch (tighter, shorter strings, shorter pipes and smaller instruments) and slower vibrations are lower frequency or lower in pitch (semi-truck driving by, looser, longer strings, large instruments).

Exponentially increasing frequencies are perceived by the human ear linearly. Notes spaced an octave apart double in frequency, but sound like they are evenly spaced.

See Pitch & Intervals for how pitches relate to one another and where the chromatic scale comes from.