When these terms are used, light is been pictured as an electro-magnetic wave.
Thinking of the microwave example, inside what you would have is like a sea where light is equivalent to the undulations. So in this picture, the wave-length is the distance between two consecutive wave peaks. Larger wave-length implies more separation between these peaks.
Also the relation between wave-length and energy is also very similar to the sea picture. Large wavelength implies the "push" you get from several waves takes is more spaced, hence you receive less total energy per time interval.
On the contrary when the wave-length is shorter, you receive the "pushes" more frequently, i.e. they are less distanced from each other, and coming one after the other more rapidly, and the transfer of energy is higher.
Finally, to clarify the classical view of light: it is an electro-magnetic wave, that is a self-sustained oscillation in space an time of electrical and magnetic fields, each of them generating the other and propagating freely through both media and vacuum.