Now mainly associated with India, but present in one form or another in many other societies East and West, any caste system (de)values and discriminates people according to their genetic and/or social background.
One should realize that the Indian caste system is not at all a clearly set convention. Not only different historical periods, but also certain regions and states vary in their application of the system and even in which group of people is regarded as higher or lower.
Counting sub-divisions, there may perhaps be 2.000 caste-groups in all. In fact, the popular idea of simply four major castes plus the so-called untouchables is more fiction than fact; especially since the latter ones (15% of society), together with India's non-Hindu tribal population (7%), are actually outside the caste system; casteless and therefore cast out. A simple breakdown of Indian society looks more or less like this:
Although caste segregation is officially illegal, it is very much alive in Indian society even at the close of the 20th century.
See, for exmple, navakanya.