Wikipedia
Purohit, in the Indian religious context, means family priest, from puras meaning "front", and hita, "placed". The word is also used synonymously with the word pandit, which also means "priest". Tirth Purohit means the Purohits which site on ford of the holy rivers or holy tanks, which maintained the records of the forefathers of the Hindu family from thousands years back.
Rajpurohit was an ancient term used to denote a priest who acted for royalty, carrying out rituals and providing advice. In this sense, it is synonymous with rajguru. Hermann Kulke and Dietmar Rothermund note that "There is much evidence in ancient texts that there were two ideal types of Brahmins in those days, the royal priest or advisor (rajpurohit, rajguru) and the sage (rishi) who lived in the forest and shared his wisdom only with those who asked for it." Its modern use in this sense has been described by Sumit Sarkar as a "self-conscious archaism".