IMF (Index mutual funds) also track baskets of securities. Unlike index funds, which are priced once after the end of each trading session, ETF (Exchange-traded funds) prices changes throughout the day because they’re traded like shares. Like shares, they can also be sold short — a bet that the index value will decline — and bought on margin using borrowed money.

You can certainly buy an IMF directly from a fund group at no “load” or sales charge. Annual management fees will typically be higher with a traditional mutual fund and you can only buy or sell at the closing price at the end of the day.

For most popular broad indexes, choosing between an ETF and an index fund depends on how much one has to invest at a time, how many funds are involved, and the commissions charged by the broker.