What does Separation of Church and State mean anyway

Separation of church and state is a political and legal doctrine that government and religious institutions are to be kept separate and independent from each other.

[1] The term most often refers to the combination of two principles: secularity of government and freedom of religious exercise.

[2]A concept often credited to the English political philosopher John Locke

[3], the phrase separation of church and state is generally traced to the letter written by Thomas Jefferson in 1802 to the Danbury Baptists, in which he referred to the First Amendment to the United States Constitution as creating a "wall of separation" between church and state.

The phrase was then quoted by the United States Supreme Court first in 1878, and then in a series of cases starting in 1947.

This led to increased popular and political discussion of the concept.