You are welcome to dig further, but to get you started, the following text is from a commonly used Internet summary overview resource (acknowledged below):
According to the IRS Publication 557†, in the Organization Reference Chart section, the following is an exact list of 501(c) American tax-exempt organization types and their corresponding descriptions.
501(c)(1) — Corporations Organized Under Act of Congress (including Federal Credit Unions)
501(c)(2) — Title Holding Corporation for Exempt Organization
501(c)(3) — Religious, Educational, Charitable, Scientific, Literary, Testing for Public Safety, to Foster National or International Amateur Sports Competition, or Prevention of Cruelty to Children or Animals Organizations
501(c)(4) — Civic Leagues, Social Welfare Organizations, and Local Associations of Employees
501(c)(5) — Labor, Agricultural, and Horticultural Organizations
501(c)(6) — Business Leagues, Chambers of Commerce, Real Estate Boards, etc.
501(c)(7) — Social and Recreational Clubs
501(c)(8) — Fraternal Beneficiary Societies and Associations
501(c)(28) — National Railroad Retirement Investment Trust
501(c)(29) — Qualified Nonprofit Health Insurance Issuers (Created in section 1322(h)(1) of the Affordable Care Act)
† 501(c)(20) and 501(c)(24) organization types receive scant mention in IRS Publication 557 and are not included in its Organization Reference Chart. 501(c)(20) organizations are no longer tax-exempt under Section 501(c)(20) after June 30, 1992, but they may request to become exempt under Section 501(c)(9) effective July 1, 1992. 501(c)(24) organizations are described as Section 4049 ERISA Trusts; Section 4049 of ERISA has been repealed. Under Section 511, a 501(c) organization is subject to tax on its "unrelated business income", whether or not the organization actually makes a profit, but not including selling donated merchandise or other business or trade carried on by volunteers, or certain bingo games. Disposal of donated goods valued over $2,500, or acceptance of goods worth over $5,000 may also trigger special filing and record-keeping requirements. Foregoing compiled by Wikipedia from IRS publications.
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