What is an S&P 500 ETF?

An S&P 500 ETF aims to track the S&P 500, a widely followed index of large U.S. companies. It's one of the most common "core" exposures investors use for U.S. equities.

Even though it's 500 companies, it can still be concentrated by market cap. The biggest companies can make up a large portion of the index, which means your exposure is heavily influenced by mega-cap performance.

When comparing S&P 500 ETFs, differences often come down to cost (expense ratio), tracking, liquidity, and how the fund manages dividends and securities lending. In many cases, the most liquid, low-cost options are very similar in outcome.