ITOT tracks the S&P Total Market Index, which covers nearly the entire investable US stock market from large caps down to small caps. Holdings are weighted by market capitalization, so Apple, Microsoft, NVIDIA, Amazon and Alphabet account for a large share of day-to-day performance. Compared with S&P 500 funds, ITOT adds exposure to mid and small-cap companies, which make up a modest portion of assets. ITOT and VTI track the total US market with different index providers and small differences in composition, so their returns have been very close. The main practical difference between them is the fund family and the brokerage platforms where each is available without commission.
