Overview
Brahmin (Sanskrit: ब्राह्मण, brāhmaṇa) is a varna, or social class, within Hindu society. The varna framework traditionally comprises four classes: Brahmin, Kshatriya (rulers and warriors), Vaishya (traders, merchants, and farmers), and Shudra (labourers).
The traditional occupation associated with Brahmins is priesthood, with practitioners often referred to as purohit, pandit, or pujari. They officiate at Hindu temples and at socio-religious ceremonies, performing rite-of-passage rituals such as solemnising weddings with hymns and prayers. Brahmins have also traditionally served as spiritual teachers, known as guru or acharya.
Within the varna order, Brahmins are accorded the supreme ritual status among the four classes. In practice, however, Indian texts indicate that some Brahmins historically pursued other livelihoods as well, including agriculture, warfare, trade, and various other occupations across the Indian subcontinent.
Within the jati (caste) system, Brahmins similarly occupy the highest position. This position is complicated by strict internal stratification among Brahmin sub-groups, as well as by historical attempts by other castes and sub-castes to challenge Brahminical dominance.
References
Adapted from the English Wikipedia article on Brahmin.