First Amendment: The amendment to the US Constitution that protects freedoms concerning religion, expression, assembly, and the right to petition. It forbids Congress from both promoting one religion over others and also restricting an individual’s religious practices.
Establishment Clause: A part of the First Amendment stating that 'Congress shall make no law respecting an establishment of religion.' This clause not only forbids the government from establishing an official religion but also prohibits government actions that unduly favor one religion over another.
Religious Freedom Restoration Act (RFRA): A 1993 federal law that ensures that interests in religious freedom are protected. It requires strict scrutiny when a neutral law of general applicability substantially burdens religious exercise.