Key Difference: VTSMX and VTSAX are terms related to funds. They are the same funds with only different classes and different expense ratios.

The VTSMX fund seeks to track the performance of a benchmark index that measures the investment return of the overall stock market. VTSMX stands for Vanguard Total Stock Market Index Investment Shares. It is can be a one-stop shop for investors looking for a domestic stock fund that invests broadly across the sectors and capitalizations. Morningstar calls the fund a core player in a portfolio, saying, "This fund's low costs, broad sector and market-cap diversification, and tax efficiency are tough to beat." Vanguard Total Stock Market Index Investment Shares has an expense ratio of 0.05 percent.

VTSAX stands for Vanguard Total Stock Market Index Admiral Shares. VTSAX is basically the fund, which was incepted in April 1992 and is managed by the Vanguard Group. The objective of the fund is to seek the investment returns of the Wilshire 5000 Total Market Index, which includes virtually all regularly traded U.S. stocks. The fund provides a convenient way to match the performance of the entire U.S. market. The funds mainly distribute dividends quarterly in March, June, September, and December. If there is any gain in capital, then they are distributed annually in December. Vanguard Total Stock Market Index Admiral Shares has an expense ratio of 0.17 percent.

Comparison between VTSMX and VTSAX:

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