The stock trading done by the exchanges through its brokers. SEBI controlled the exchanges. The brokers are appointed by the exchanges with huge amount of deposits. the buyers and sellers can do the business only trough brokers. Share prices are decided by the traders. The exchanges has gives a chance to the traders to modify their buy or sell orders or cancell their orders. there are two types are trade 1.positional trade and the second one is intraday trade. In these exchanges we can sell the stocks without ownng it and it should be bought before closing of the exchange. we should have a good trade plan to do trading in the stock exchange.