We know that a disturbance causing energy transfer from one point to another is called a wave.
Wave frequency means the number of waves passing through a point per unit of time.
Or we can say wave frequency is the number of oscillations made by the wave per second.
The unit for wave frequency is hertz (Hz).
The frequency term can be easily explained by taking an example of a coil of a slinky which is moved by completing two cycles in one second. The rate of it is motion is 2 cycles/second. Hence its frequency is 2Hz.