A limited company in the United Kingdom is a corporation whose liability is limited by English law or Scots law. There are three main types of limited companies which are set up by the Memorandum of Association & Articles of Association:
As a shareholder in a limited company, if it were to go bankrupt, you would only be liable to contribute the amount remaining unpaid on the shares (usually zero, as most shares are issued fully paid). 'Paid' here relates to the amount paid to the company for the shares on first issue, and shouldn't be confused with amounts paid by one shareholder to another to transfer ownership of shares between them. Being a shareholder means you have limited liability.
A limited company can be registered in England and Wales, Scotland or Northern Ireland. The registration of companies in Great Britain (England, Scotland and Wales) is done through Companies House. The registration of companies in Northern Ireland is done through the Department of Enterprise, Trade and Investment (DETI).