The Nasdaq-100 Index is a stock market index that includes 100 of the largest non-financial companies listed on the Nasdaq Stock Market. It represents a diverse range of industries, including technology, consumer services, and healthcare, making it a key indicator of the performance of the U.S. economy. Investors often use the Nasdaq-100 to gauge the health of the technology sector, as many prominent tech companies, such as Apple, Microsoft, and Amazon, are part of this index. The index is weighted by market capitalization, meaning larger companies have a greater impact on its overall performance.