The Nifty 100 index is a broad-based benchmark index in India.It represents the performance of the top 100 companies listed on the National Stock Exchange (NSE).The index includes companies from various sectors and is designed to provide a snapshot of the overall market performance.

100 companies listed on NSE based on free-float market capitalization are part of Nifty 100.

The top three sectors of Nifty 100 index are Finance with weightage of 9.00%, Banks with 8.00%, Automobile with 7.00%.

The Nifty 100 index is a market capitalization-weighted index. This means that the weight of each stock in the index is determined by its market capitalization, which is calculated by multiplying the stock's price by its total number of shares outstanding. The higher the market capitalization of a company, the greater its weight in the index. This ensures that larger companies have a larger impact on the index's performance compared to smaller companies.

You can invest in Nifty 100 index by investing in ETFs that follow this index. Top three ETFs that follow Nifty 100 index are ICICI Prudential Nifty 100 ETF, LIC Nomura MF ETF - Nifty 100 and HDFC Nifty 100 ETF.