The "Net Profit" is the earnings result from a business operation during a fiscal period (which is normally a year). this profit is divided proportionately among the shareholders of the company. A shareholder is an individual who was bought a certain number of shares, which are the right to ownership of a percentage of the company.
A business is its legal right to retain yearly earnings (the net profit) if that is the decision taken by the board or the owners. This is a common practice in order to reinvest the earned money in the business in order for it to grow.