The nonprofit sector in the United States contains a whole variety of organizations, including hospitals, human service organizations, credit unions, universities, professional sports leagues, cultural institutions, electric co-ops, trade associations, foundations, and a variety of others.
However, when people mention "charities", they usually mean only a subset of these. So we defined "nonprofit" as any entity tax-exempt under the IRS, and "charity" to mean 501(c)(3) organizations that can receive tax-deductible contirbutions, excluding hospitals, colleges, universities, insurance companies, and their respective foundations.