What is a fund fee?
Fund fees are what a fund manager charges each year, usually as a percentage of your balance plus any fixed dollar fee.
Fees come out every year whether returns are good or bad, so small differences compound. Index funds and ETFs usually cost less than actively managed funds.
Example
On a $200,000 balance, a 1% fee costs $2,000 a year, while a 0.25% fee costs $500.