Well, what is a wave?: A wave is an undulating (rolling and falling) disturbance that moves across the sea surface.

Now, waves form and dissipate (go away) as a result of disturbing forces: The most common disturbing force is energy transferred to the sea surface by the wind.

Other disturbing forces could be earthquakes, landslides, and volcano eruptions. They can trigger very large waves like tsunamis.

Waves are complicated phenomena. For example, when a wave travels, it propagates energy but there is no real transfer of mass. The wave size depends on the wind speed, the length of time that the wind blows and the distance over which wind and water interact. Obviously, the faster and longer the wind blows, the bigger the waves and the more energy they possess.