Reg3e OP : Learn. Trade. Win

Reg3e OP Jackie Hampton : It means investing in a broad market ETF such as VT. It hold thousands of stocks worldwide, so you're diversified across global companies, reducing the risk of being stuck with individual companies, sector, or country performing poorly.
Since ETF like VT is based on Market Cap, poor performing companies will automatically hold less % in your portfolio, while those performing well will gain more % in your portfolio, as reflected in their company growth/market value.