The Sensex index, officially known as the S&P BSE Sensex, comprises 30 of India's largest and most actively traded companies listed on the Bombay Stock Exchange (BSE). These companies represent a diverse range of sectors, including finance, technology, consumer goods, energy, and healthcare, making the Sensex a key benchmark for the Indian stock market.

The 30 companies in the Sensex are selected based on factors such as market capitalization, liquidity, sector representation, and trading frequency. The index follows a free-float market capitalization methodology, meaning that companies with a higher proportion of publicly traded shares have a greater influence on the index's movement.

The composition of the Sensex is reviewed periodically to ensure it remains a true reflection of market conditions. Companies that no longer meet the required criteria may be removed, while new, high-performing companies can be added.

Since its inception in 1986, the Sensex has served as a barometer of the Indian economy, tracking market trends and investor sentiment. Traders, investors, and analysts widely use it to assess the overall health of the stock market and make informed investment decisions.