White noise is a static sound that has equal energy on every frequency. Think about this for a second: every frequency from 20Hz to 20kHz is equally represented at the same velocity; this type of frequency scale is called a "linear" scale. This gives the noise a uniform, static sound that the human ear detects as somewhat harsh and heavy-handed toward the high frequencies. However, white noise represents a very unnatural way of presenting frequency data in terms of how our ears work.
Pink noise is similar, except that you have to think in terms of octaves. Pink noise is equal energy per octave, rather than equal energy per frequency. Pink noise has a -3dB per octave slope, which makes the spectrum look completely flat on a logarithmic scale. Pink noise, to the human ear, sounds much more natural -- and the human ear is able to discern frequencies in the low, mid, and high ranges.
Pink noise is very useful for tuning audio equipment and calibrating studio monitors, microphones, and speakers.