Pigmentation

Pigment mean is dot of color and here the pigmentation mean color of skin. People leaving at the equator have different color than the people leaving the region situated at the pole of earth .Because there are different levels of intensity of sunlight on different parts of the earth. Region where sunrays would be more intense there would be more production of melanin in the body and as quantity of melanin increases in the body it increase the darkening of skin..
There are many pigmentation disorder and most common among them Vitiligo.

Hyper-Pigmentation

Darkening of skin as compare to the surrounding area is termed as the hyper pigmentation. It is a two fold term. Two in the such a way
When in normal condition and for health skin when some dark patches appear it would be treated as a skin condition.
In vitiligo skin condition when white patches appear on the skin. Then treatment are applied to hyperpigmentation of the depigmented(vitiligo affected) are of skin.
Here hyper pigmentation is for treatment of skin condition.

Depigmentation

Loss or Lack of pigmentation in the skin is termed as depigmentation. Suppose when white patches of vitiligo skin condition appears on skin it is said patches of depigmentation. Beside vitiligo there are some other skin condition that also causes the depigmentation in skin like vitiligo.

Vitiligo

Vitiligo is pigmentation disorder causing depigmentation in skin by giving white patches on skin. No other skin condition for which people want pigmentation back than vitiligo. Also No other skin condition is as serious as this. Because real causes of vitiligo are not fully know and treatment of vitiligo normally take very long period and some time give not result.

Some other skin conditions which are also related to the depigmentation are as under:
White scars and hypopigmentation
Nevus depigmentosus
Pityriasis Alba
Idiopathic guttate hypomelanosis