The Establishment Clause of the First Amendment prohibits government from encouraging or promoting ("establishing") religion in any way. This means that the government may not give financial support to any religion.
That's why many school voucher programs violate the Establishment Clause -- because they give taxpayers' money to schools that promote religion.
The Free Exercise Clause of the First Amendment gives the right to worship or not as you choose. The government can't penalize you because of your religious beliefs.
The Establishment Clause has generally been interpreted to prohibit (1) the establishment of a national religion by Congress, or (2) the preference by the U.S. government of one religion over another.
The first approach is called the “separation” or “no aid” interpretation, while the second approach is called the “non-preferential” or “accommodation” interpretation.
The accommodation interpretation prohibits Congress from preferring one religion over another, but does not prohibit the government’s entry into religious domain to make accommodations in order to achieve the purposes of the Free Exercise Clause.
For further reading, go to:
www.aclu.org
harvardpolitics.com
[courses.lumenlearning.com](https://courses.lumenlearning.com/boundless-politicalscience/chapter/the-first-amendment-the-right-to-freedom-of-religion-expression-press-and-assembly/