Private Limited Company by Shares
Many businesses will reach the stage (both physically and financially) where it is more beneficial to operate through the mechanism of a limited company rather than as a sole trader or in a partnership.
A limited company is a separate legal entity, it is owned by its members (shareholders), it must be registered at Companies House and adhere to certain accounting and filing requirements as well as company legislation most particularly the Companies Act 2006. Company and personal finances are kept separate and so unlike sole traders (or partners), its directors and shareholders have 'limited liability' in that their personal assets cannot be touched - unless they have given a personal guarantee. Limited companies are subject to corporation tax on their profits.
If you want to set up a joint venture, obtain a business bank loan, split the ownership and management of a business, enter into contracts – but not in a personal capacity and distance your personal assets.