The difference between a long and short wavelength is the distance between two identical points on successive waves. Wavelength is also characteristic of the energy level of a particular wave, with shorter wavelengths being more energetic than longer ones.
Wavelengths are typically measured from the peak or trough of one wave to the same point on the next wave in the cycle. This is also a measure of frequency, which is the amount of wavelengths passing by a given point over the course of one second. Wavelengths have been classified according to their lengths, with audible waves and radio waves at the longer end of the spectrum and X-rays and gamma rays at the shorter end.
Differences in wavelengths can also be seen with the naked eye in the form of visible light. Shorter visible light waves correspond to specific colors, such as blue and purple, while red and orange have longer wavelengths. The white light that the human eye registers is simply a mix of all of the respective wavelengths of visible light. The wavelengths of light, just as those within the audible spectrum, go far beyond what is detectable by human senses, with infrared and ultraviolet wavelengths as two examples from opposite ends of the spectrum.