If a business owner has "limited liability," it means that he or she is not personally responsible for business debts and obligations of the corporation. In other words, if the corporation is sued, only the assets of the business are at risk, not the owners' (shareholders) personal assets, such as their houses or cars. The corporation's owners must comply with certain corporate formalities, keep up with paperwork requirements, and adequately fund ("capitalize") their business to maintain this limited liability privilege. For more information, see Nolo's article Corporation Basics.
Limited liability, traditionally associated with corporations, is the main reason most people consider incorporating. However, other business structures, such as limited liability companies (LLCs), now offer this limited personal liability to business owners. Sole proprietorships and general partnerships do not.