A social enterprise is any for-profit or non-profit organization that applies capitalistic strategies to achieving philanthropic goals. Many commercial enterprises would consider themselves to have social objectives, but commitment to these objectives is fundamentally motivated by the perception that such commitment will ultimately make the enterprise more financially valuable. Social enterprises differ in that, inversely, they do not aim to offer any benefit to their investors, except where they believe that doing so will ultimately further their capacity to realise their philanthropic goals.
Many entrepreneurs, whilst running a profit focussed enterprise that they own, will make charitable gestures through the enterprise, expecting to make a loss in the process. However unless the social aim is the primary purpose of the company this is not considered to be social enterprise. The term is more specific, meaning 'doing charity by doing trade', rather than 'doing charity while doing trade'. Another example is anuncorporation, which may pursue social responsibility goals that conflict with traditional corporate shareholder primacy, or may donate most of its profits to charity.
More on: http://en.wikipedia.org/wiki/Social_enterprise