An index is a tool that measures market movements, tracks sector performance, and acts as a benchmark. There are two main ways to calculate an index: price weighted, which weights stocks by price, and market capitalization weighted, which weights by market share. Some key global indices are the Dow Jones, S&P 500, Nikkei 225, and Sensex. In India, the two major indices are the Sensex and Nifty 50. The top constituents of the Nifty 50 are HDFC Bank, Reliance, HDFC, and Infosys. Sectoral indices track performance by industry. The financial services sector has increased its representation in the Nifty over time. Indices are rebalanced through reconstit