Stock market is the exchange of securities of listed companies between buyers and seller.Buyer searching for good seller(who sell in low price among all).Seller searching for good buyer(who willing to buy share in high price).shareholders are the ownership of particular company.It is secondary market.IPO is example of primary market.In India ,NSE and BSE exachange.NIFTY overall performance of listed companies in NSE.It is calculated by top 50 companies among above 1800 companies.SENSEX is the calculation of average performance top 30 companies among above 3000 companies. SEBI establish guideline for the regulators for the company and SEBI registered brokers.