We experience frequency as a range of Pitches from low (around 50 Hz) to high (around 20,000 Hz).
Of course, not one, but many molecules are involved, and as they hit the next molecule layer as a group, we have a band of compressed air, followed by a band of rarified air.
This band expands in all directions like a balloon. And since the process is repeated, it is really more like an expanding balloon within a balloon within a balloon etc. Each balloon represents one cycle per second (cps).
Not that anybody calls it cycles per second anymore. In this age of high technology, that was too simple, so they changed it to Hz, in honor of a German physicist (Von Hertz).
Oscillating is what the molecules of air are doing, and that is called Frequency. How we experience or perceive it is called Pitch. Our ears can detect a range of pitches from as low as 50 cps (excuse me, Hz) to around 20,000 Hz.
NOTES: See some Technical information on Pitch.