A 501(c)(3) organization is a corporation, trust, unincorporated association, or other type of organization exempt from federal income tax under section 501(c)(3) of Title 26 of the United States Code. It is one of the 29 types of 501(c) nonprofit organizations in the US.
501(c)(3) tax-exemptions apply to entities that are organized and operated exclusively for religious, charitable, scientific, literary, or educational purposes, for testing for public safety, to foster national or international amateur sports competition, for the prevention of cruelty to children, women, or animals. 501(c)(3) exemption applies also for any non-incorporated community chest, fund, cooperating association or foundation organized and operated exclusively for those purposes. There are also supporting organizations—often referred to in shorthand form as "Friends of" organizations.
501(c)(3) organization Facts for Kids. Kiddle Encyclopedia.