Waves are travelling disturbances that transfer energy from one place to another. They do not transfer matter. The amplitude of a wave determines its energy. Higher the amplitude, higher is its energy. Sound, light etc are all different kind of waves. They can be classified in different ways based on their characteristics. One such classification is as electromagnetic and physical waves.
Electromagnetic waves do not need a medium to travel. They can travel through vacuum. When we listen to the radio, watch television or use microwave oven, we are using electromagnetic waves. The EM waves include radio waves, microwaves, infrared waves, visible light, ultraviolet waves, x rays and gamma rays.
The other kind of waves that need a physical medium like air, water etc is called physical or mechanical waves. These waves travel when molecules in the medium collide with each other passing on energy. Examples include sound waves, water waves, seismic waves (earthquake waves), and waves traveling through a spring.
Waves come in various shapes and sizes. Based on their observable characteristic like direction in which the disturbances are travelling, it can be classified in three ways – longitudinal, transverse and surface waves.
Transverse wave is a wave in which the particles of the medium move in a direction perpendicular to the direction in which the wave moves. Water waves seen in the beach are transverse in nature. All electromagnetic waves are transverse waves.
When the particles of the medium travel in the same direction as that of wave propagation is called longitudinal waves. Sound waves are longitudinal in nature.
There are also surface waves that travel in circular motion like that of waves in the ocean and ripples in the water. The particles of the medium undergo a circular motion. These waves are a combination of transverse and longitudinal waves.