The AEX, or Amsterdam Exchange Index, is a stock market index that represents the performance of the 25 largest and most actively traded companies listed on the Euronext Amsterdam. It serves as a key indicator of the overall health of the Dutch stock market and is widely followed by investors. The AEX is calculated based on the market capitalization of its constituent companies, which include well-known firms from various sectors, such as Unilever and Royal Dutch Shell. Changes in the AEX reflect the collective performance of these companies and can influence investment decisions in the region.