Wave Type (Direction of Oscillation)

When a wave moves along a rope (for example) from left to right, as in figure 4, the rope particle moves back and forth in a cross-directional (i.e., vertical) direction against the wave movement itself, which is called a transversal wave.
It is called a longitudinal wave when the oscillation of the medium particle is along the direction of wave movement. 
A series of compressions and expansions run along the length of the spring. Compression is the area where the coils are momentarily close together. Expansion, or stretching, is the area where the coils are momentarily far apart. Compression and expansion are the same as the peaks and troughs of transverse waves.