A mechanical wave requires a medium to travel
When waves travel, they are accompanied by the transfer of energy
This energy propogates in the same direction in which the wave is travelling
An example of a mechanical wave is a wave in the sea or a sound wave
Because energy cannot be created, these waves require an initial energy input
If the energy input is just applied once, a disturbance of particles occurs at the source
However, for a transverse wave if the disturbance at the source continues, the wave is maintained
A good way to visualise this motion is a bead on a string that is being shaken at one end, and is fixed at the other
If you apply a simple harmonic force to the rope in a virtical direction, you will produce a sine wave
This is beause the only thing that moves in the wave is energy