If you've been an investor for any length of time at all, then you've almost certainly been advised to start (and maybe even finish) with index funds like the Vanguard S&P 500 ETF. This fund is of course simply meant to mirror the performance of the S&P 500.

If you're new to investing and don't have a lot of money to get started, don't fret. The best place for new investors to begin is often with exchange-traded funds (ETFs), which will give investors instant diversification through a portfolio of stock holdings.

As market-capitalization-weighted index ETFs, both VOO and VTI naturally feature a high allocation to large-cap stocks. If you want to focus more on mid- and small-cap stocks, a dedicated non-core ETF like VXF might be ideal. This ETF tracks the S&P Completion Index for a 0.06% expense ratio.

Vanguard is one of the gold standards when it comes to low-cost exchange-traded fund (ETF) options. Undoubtedly, passive investing (typically with index funds) tends to be wildly popular among the retail crowd.