Companies can collect funds from the public to expand their business or to enter in to new field. Those who gives money called share holders. The place where these things usually happen is "Share Market". There are two markets available 1.Primary market - where Initial Public Offer takes place. Companies directly sell their share to the public. 2. Secondary market - where buying or selling of shares takes place. People those who hold shares of particular company can sell their shares and people who wants to buy shares can get from here. This share markets are controlled by Government. If some one wants to trade in share market then they should have Demat account with any one bank. They should have PAN card with them. You can also do intra day trading if you get a permission to do so. One should get good knowledge about this before get in to trading to avoid any loss.