What does separation of church and state mean?

It’s common today for people to state the phrase “separation of church and state” and attribute it to the United States Constitution, but it will not be found there.
This popular phrase was something that Thomas Jefferson used in an 1802 letter to the Danbury Baptist Association, according to mtsu.edu. In the letter, Jefferson declared that, when the American people adopted the establishment clause, they built a “wall of separation between the church and state.” But the creator of this phrase was not Jefferson, it was Roger Williams. Roger Williams was the first public official to use this metaphor.
But what is the true meaning to “the separation of church and state”? To put it simply, most people know by now not to mix politics with religion when conversing. “Separation of church and state” represents not mixing religion and politics, according to TIME. It wasn’t until 1879, however, when the Supreme Court first employed the term “separation of church and state.”
Matter of fact, “Separation of church and state” is an extremely misunderstood phrase. As ERLC states, to clear up false rumors, the term does not mean separation of moral reasoning from public policy, nor does it mean a separation of religiously informed moral reasoning from public policy. “Separation of church and state” is a foundational principle which secures the rights and privileges of all citizens under a government and ensures that both government and church function accordingly to their God-given roles.
What the United States Constitution does say about religion is in the First Amendment, where it states “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof…”, meaning that the government cannot require citizens to follow a particular religion or keep them from practicing it in a way that is deemed appropriate.