Running a social enterprise is not very different to running a normal business as a social enterprise can trade in goods and services, can make a profit, employ people and pay salaries. The only real difference is that any profit made must be used to further the social aims of the business.
Social enterprises compete in the market place like any other business, but they use their business skills to achieve social aims.
Social Enterprise Coalition
"A social enterprise is not defined by its legal status, but by its nature: what it does that is social, the basis on which that social mission is embedded into the business, in its structure and governance, and the way that it uses the profits it generates through its trading activities."
Jonathon Bland - Chief Executive, Social Enterprise Coalition
“My own experiences with some of the dynamic social enterprises already operating around the UK has convinced me and my colleagues in Government that there is now a significant opportunity to promote radical new ways to boost our economy and society through the social enterprise approach”
The Right Honourable Tony Blair, MP, Prime Minister
"It doesn't matter what you call yourself, just be absolutely bloody great at what you do. If you want to trade in competitive markets, good for you ........ If you don't or can't, and you will continue to fund raise to stay in business - great. The point is not that we settle for the creation of lots more social enterprises of particular legal forms, or that we have schools and hospitals run by social businesses. Our ambition must be bigger than that. To deal with the challenges we face, we must get better at learning from one another, building alliances."
Liam Black - head of Jamie Oliver's Fifteen group of social enterprises

"Social enterprises are businesses that combine trading in the market place with social objectives. They require a structure that enables them to trade whilst minimising the risk to the organisation and its members, and that ensures that the organisation will operate in an ethical manner.
Some legal structures designed for the use of coventional capitalist businesses, (e.g. sole traders, partnerships, companies limited by shares and plcs) are not appropriate for social enterprises except in rare circumstances. Equally, some legal structures designed for social purpose, (I.e. charities and trusts) cause significant problems for social enterprises because they are not designed to enable trading activities. Finally, there are a number of structures for social enterprises which are only appropriate in very specialised instances (i.e. building societies, credit unions and friendly societies)." - Dave Hollings, CMS
The attached is a simple guide to the different types of structures that are available to enterprises.
Legal Structures Guide (PDF 72kb)