VOO, the Vanguard S&P 500 ETF, is a popular choice for broad U.S. equity market exposure, tracking the S&P 500. With a low expense ratio of 0.03%, it's cost-effective for long-term investors seeking diversification across major sectors. The ETF's structure provides tax efficiency, essential for reducing taxable gains. However, VOO's heavy weighting in tech giants can lead to volatility in downturns specific to that sector.