A caste system is a type of social structure which divides people on the basis of inherited social status. Although many societies could be described in this way, within a caste system, people are rigidly expected to marry and interact with people of the same social class. India has a well known example of a caste system, although various forms of caste systems can be found in many other cultures as well.
Several characteristics distinguish a caste system. The first is the tendency toward endogamy, meaning that people marry within the same caste exclusively. Caste mobility is also extremely rare; one cannot transform from a laborer to a scholar except in very rare circumstances, for example. Higher castes traditionally hold all of the political power, and the castes may be divided further through language, culture, and economics. Within a caste system, each member generally knows his or her place, and your social status is usually apparent to others as well.
Although people associate the caste system with India, the word is actually borrowed from the Portuguese. By 1555, English speakers were using the word to refer to a race of men, adopting the Portuguese word casta. Although the word was used in English to describe race or breeding, in Portuguese it was more widely used in reference to the stratified society of Portugal. When the Indian social system was encountered in the 1600s, it came to be described as a caste system in the Portuguese sense.
The roots of the Indian caste system can be found in the Hindu scriptures, although the caste system was adopted by other religions in India as well. According to scripture, Indian society could be broken down into a number of different groups, known as Varnas. Brahmins, the highest caste, were scholars and priests, while Kshatriya were warriors, rulers, and landlords. Vaisya were merchants, while Sudra were manual laborers. Beyond there four basis Varnas are the Untouchables or Dalit, and the system also has a space for outsiders and foreigners who do not conform with the system.
Within each Varna there are hundreds of Jati, individual endogamous groups. India's extremely refined and complex caste system began to be reformed during the push for independence, and technically discrimination on the basis of caste status is not allowed in modern India. However, the remains of the caste system can still be seen in the way that Indians move through and interact with their society. Many people of lower caste, for example, face legal barriers and difficulty when they try to enter Indian politics.