If your retirement is 10 or more years away, the funds that fit best are usually a broad US or world stock index ETF plus a broad bond ETF, held at a ratio that matches your horizon. Closer to retirement, a short-term inflation-protected bond fund and a T-bill fund often join them. The tickers matter less than people think: VOO, IVV and SPYM all hold the S&P 500 index, and VTI, ITOT and SCHB all hold close to the whole US market.
Scope. This guide covers US-listed ETFs for US savers using a 401(k), IRA, Roth IRA or taxable brokerage account. It does not cover individual stocks, annuities, crypto held directly, or non-US accounts. It is education, not personal advice: the right mix depends on your spending, other income, taxes and how you react to losses.