Figure: Illustrations of transverse and longitudinal waves propagating through media

Image 1 Caption: An illustration of transverse waves (each wave being one complete up-and-down cycle) propagating in one direction. The image is generic for transverse waves, but it is NOT particularly good for illustrating electromagnetic waves (which are transverse waves).

The labeling in the image seems to be Russian.

Further explication:

1. Note, a wave form with a complete up-and-down cycle has a length called a wavelength. The universal symbol for wavelength is the small Greek lambda = λ.

2. In the case of transverse waves, the propagation direction and oscillation direction are perpendicular.

   Examples of transverse waves are electromagnetic waves and waves on a string.

   

3. Image 2 Caption: In the case of longitudinal waves, the propagation direction and oscillation direction are parallel.

   Longitudinal waves usually consist of compressions and rarefactions of density, and these are often accompanied by waves of high and low pressure regions.

   The main example of longitudinal waves are sound waves which are always longitudinal in fluids, but can be either longitudinal or transverse in in solids.

4. There are, in fact, combinations of transverse waves and longitudinal waves: the most well known example is surface water waves.