Frequency is the number of occurrences of a repeating event per unit time.
Example of frequency waveforms
Frequency chart showing different Hz waveforms
We have a limited range of frequencies that we can hear. Commonly it is from 20 – 20,000 Hz (Hertz) though this varies in individuals and we would expect higher frequncy loss with age.
So the frequency denotes the pitch of the sound that we can hear.
The wikki page here has a nice table showing the various frequencies for various notes and octaves.
Frequency Chart 1
Soundonsound Frequency chart
Matt Cooper 