What’s the difference between investing in a S&P 500 index fund vs a S&P 500 ETF?

I'd recommend investing in an S&P 500 ETF! To my knowledge, ETFs have a lower expense ratio (e.g. VOO has an annual expense ratio of only 0.04%). Also, since ETFs are bought and sold like stocks, it's more liquid than Index Funds which are only bought/sold after the market closes. There's a more in-depth article here if you want to know more: https://www.fool.com/investing/2016/08/26/etf-v...