What type of wave has particles push together and pull apart?

when wave propagate through the medium the medium particles have two type of possible motions

1) Transverse Waves : here medium particles will move perpendicular to wave propagation and they pull and push perpendicular to the length

2) Longitudinal wave : here medium particles will move to and fro along the length of the medium and the medium particles will push and pull together along the length of the string.

So here in two types of wave motion it will depends on the medium type as well as it will depend on the source how is wave produced.

So the given type of wave in which particles push together and pull apart the wave must be longitudinal wave.

truck y has a greater velocity than truck x.