Ignorance of the nonprofit sector — especially its scope and diversity — is rampant and has been a topic of increasing concern to me over the nine years I have been in my role at CEP. This brief video is the best quick overview of the sector I have seen and I hope it is used to help address this issue:
For a good discussion related to this video, and the criticism of the Giving Pledge that is rooted in ignorance of the sector, check out Tactical Philanthropy.