The most common type of nonprofit organization, this IRS category covers a lot of ground.
A 501(c)(3) nonprofit is exempt from federal income tax if it has these purposes:
charitable, religious, educational, scientific, literary, testing for public safety, fosters amateur sports competition, prevents cruelty to children or animals.
Examples of qualifying organizations include old-age homes, parent-teacher associations, charitable hospitals, alumni associations, schools, chapters of the Red Cross or Salvation Army, Boys' or Girl's clubs, and churches.
501(c)(3) organizations may receive grants from foundations; and donations to them are tax-deductible for the donors.
IRS publication 557 contains information on qualifying for and applying for 501(c)(3) status.