This document provides an introduction to non-profit organizations (NPOs) and social enterprises. It defines NPOs as organizations that exist to promote public welfare rather than earn revenue, and are often tax-exempt. NPOs, also called the third sector, include charities and voluntary organizations. They are driven solely by social goals and rely on donations, while social enterprises have both social and financial goals, using earned income to be sustainable. The key differences between social enterprises and NPOs are discussed.