Insured bank products (savings tier)
The big-bank default. Insured (FDIC/NCUA up to $250,000 per depositor, per bank, per category) but often pays nearly nothing — 0.1%-style rates are common at large branches.
Online banks paying multiples of the branch average. Identical insurance, no branch, 1-2 day transfers. The standard emergency-fund home.
A bank account with savings rates and limited check/debit access. Insured like any deposit — do not confuse with money market FUNDS.
Lock money for 3-60 months for a fixed rate, usually above savings. Early exit costs interest. Best for known-date goals and emergency-fund ladders.

Government-backed market instruments
Short-term loans to the US government (4-52 weeks), bought at TreasuryDirect.gov or via brokers. Backed by the government, exempt from state income tax, rates track the market.
Investment products (different animal — can lose value)
Brokerage funds holding T-bills and similar; yield floats daily; NOT insured. Government/Treasury flavors are the conservative standard. Full guide: What is a money market fund?
The container for stocks, bonds, ETFs and funds. No insurance against market losses (SIPC covers broker failure, not price drops).
Long-term growth tools with real down years. Explained plainly in Beyond the Emergency Fund.
Tax-advantaged wrappers around investments, with contribution limits and early-withdrawal rules set by the IRS — verify current-year numbers at irs.gov.
Bronnen: FDIC — Deposit insurance · TreasuryDirect — Treasury bills · IRS — Retirement plan contribution limits