Nifty 50 is the National Stock Exchange's flagship index. It tracks 50 of the largest and most liquid companies listed on NSE, spread across sectors such as banking, IT, energy, FMCG and autos, weighted by free-float market capitalisation. When people say the market went up today, they usually mean Nifty or Sensex rose. You cannot buy the index itself, but you can buy a Nifty index fund or ETF, or trade Nifty futures and options, which are the most heavily traded derivatives in India. A one-point move in Nifty changes a one-lot position by the lot size in rupees. The index is reviewed twice a year, and companies are added or dropped. Nifty's level, say 24,000, is not a price in rupees; it is a number relative to its base value of 1,000 in 1995. Its daily change in percent is what matters.