In basic terms, if you are the sole owner, you can operate as a sole trader or you can form a limited company. If your business has more than one owner, you can operate as a limited company, a partnership or a limited liability partnership.
The most suitable form for your business will depend on a number of factors: what kind of business you have, how many people are involved, how you intend to structure the internal management of your business, tax liabilities, profit distribution, and whether you intend to remove profits and reinvest them back into the business.
If you are at the stage of moving your business from idea stage to starting up, you should seriously consider getting expert legal and financial advice. The best time to get advice from your lawyer and accountant is before you set up and register the business, before you open a bank account, and before you start taking on customers.