From The Art and Popular Culture Encyclopedia
A parish is a territorial unit that was usually historically served by a local church. This ecclesiastical administrative unit (see Civil Parish) is typically found in these Churches: Roman Catholic, Anglican Communion, the Eastern Orthodox Church, the Church of Sweden, the Church of Norway, some Methodist, and Presbyterian churches. It refers to a local, ecclesiastical community or territory, including its main church building, perhaps one or more chapels of ease and other property. The word "parish" is also used more generally to refer to the collection of people who attend a particular church. In this usage, a parish minister is one who serves a congregation.
In some countries a parish (then more precisely a "civil parish") is (also) an administrative area of civil government. Parishes of this type are found in England, Ireland, the Isle of Man, the Channel Islands, the U.S. state of Louisiana, and a number of island nations in the region of the Caribbean. In general they originate from an ecclesiastical parish of the same name perhaps, in the course of time, with modified boundaries to better suit local government.