Index funds and exchange-traded funds (ETFs) are very similar; both are pooled investment vehicles that offer diversified access to an asset or a group of assets. Most index funds are structured as open-ended funds, but some closed-ended funds exist. An open-ended fund trades at prices determined by the fund’s net asset value at the end of each trading day, while a closed-ended fund trades throughout the day at fluctuating market prices. Whereas, all ETFs trade throughout the day at fluctuating market prices.