the ultimate reason why people take up Stock trading is too make money. and it can be done through a Stock exchange. Stock exchange is a place where buyers and sellers meet to buy and sell shares. This can be done through a broker only. the broker acts as a bridge between the buyer/seller and the exchange.. The exchange is responsible to honour every transaction. The stock price is based the DD and SS prevailing in the market. Stock trading is a business because the risk to reward ration can be calculated with the available knowledge.