what is an index fund 
an index fund is a type of mutual fund or etf with a portfolio constructed to track the components of a financial market index such as the russell 3000 the bottom linethe russell 3000 index established in 1984 measures the performance of the largest 3 000 u s companies representing approximately 96 of the investable u s equity market large cap stocks direct the index s performance and include holdings such as apple microsoft and meta 1