Stock Market is where shares of pubic listed companies are traded. Stock Market is of two types, Primary Market and Secondary Market. Primary Market is investors buy equity shares directly from the company through IPO for first time. Secondary market is investors trade shares ( Buy and Sell ) among themselves through Stock Market.
The Sensex and Nifty are “indices of a indian stock market”.
Nifty is calculated by taking the average of top 50 companies traded in National stock exchange.