Question

what is mean by wave

Answer 1

move to and fro with a swaying motion while remaining fixed to one point is called wave.
 wave can be described as a disturbance that travels through a medium from one location to another location.

Answer 2

Wave is a disturbance that propagates with respect to time through a medium or empty space. Waves are basically of two types: transverse wave and longitudinal wave.

Hope it helps :)