501(c)(3) organization

Definition 
A 501(c)(3) organization is a non-profit organization based in the United States who doesn't have to pay taxes because it falls under Section 501(c)(3) of the United States code.

Entities that are formed and run solely for religious, charitable, scientific, literary, or educational purposes, for public safety testing, to promote amateur sports competition on a national or international level, or to stop cruelty to children or animals are exempt from taxes under Section 501(c)(3).  

Additionally, any non-incorporated communal chest, fund, cooperating association, or foundation established and run specifically for such purposes is included under the 501(c)(3) exemption.  Supporting groups are also available; these are frequently abbreviated as "Friends of" groups.

References

Category:Taxation in the United States
Category:Non-profit organizations of the United States