The pitch of a sound is the ear and brain interpreting the frequency of the sound. When there is a high frequency, the ear interprets the sound as a higher pitch, and when the frequency is low, the ear hears a low pitch. Pitch has been standardized and uses "cents" as a unit of measurement.
The pitch of a sound can simply be thought of as a measure of the sound's frequency. For example, when an instrument plays different notes, they are more accurately different pitches. These pitch differences are actually just the ear and brain's perception of the instrument emitting different frequencies.