An index is a measure that tracks the performance of a specific group of assets, such as stocks, often representing a particular sector, industry, or the overall market. Stock indices combine the stock values of multiple companies into one composite figure, providing a quick snapshot of market trends and helping investors gauge market health without analysing individual stocks. Stock indices are popular because they offer a clear, accessible benchmark for investors to compare individual investments, assess overall economic performance, and identify trends, all of which can inform investment decisions and provide insight into market sentiment.