Private limited companies are actually independent business entities. Its shares are not displayed on the stock exchange. Simply putting, it is like a small retailer in town. This kind of business offers only limited legal protection to its shareholders which also results in some rules. Often such companies incorporate these rules into their regulations so as to ensure no illegal takeover.
Except for share on the stock exchange, private limited companies can be issued to raise capital, the business owners have limited liability and the business continue on even after death of the shareholders. This is what sets private companies apart from public companies.