Stock market is a place where people buy and sell stocks. Companies raise capital in stock market. A comapny becomes public limited when it decides to raise capital from public. The company announces IPO and is assigned a share value. The value of the share prices vary with respect to demand and supply. Share holders can earn money through dividends and selling the stock at higher price. The buying and selling of securities take place in stock exchanges through brokers. It is regulated by SEBI.