The frequency of a watch movement signifies the number of oscillations the movements balance makes per second, measured in hertz (Hz). The oscillations of the balance become more precise at higher frequencies.
The ticking sound of a watch is caused by the oscillations of the balance.
Quartz watches often have a frequency of 32 Mhz while mechanical watches are usually significantly lower.
These days producing higher frequency movements has become the goal of many watchmakers.