Role of Broker help us to buy or sell a stock, they charge brokerages for that.
Stock exchange is an organisation which ensures the stock brokers to trade in behalf of share traders.
SEBI is the regulation board for the stock market.
People choose stock trading to invest or trade on a company in order to increase their capital. The price of a stock is decided by the number of traders trade a company. There are two type of trading positioning and intraday. Stock price does not affect the company it remains with the traders.