Tax-Deferred
Growth you're not taxed on until you withdraw — the defining feature of traditional 401(k)s and IRAs.
Tax-deferred means you postpone the tax. Contributions to a traditional 401(k) or IRA may reduce taxes today, the investments grow without annual tax drag, and you pay ordinary income tax only when you withdraw in retirement. The bet is that deferring lets more money compound and that you'll withdraw at a lower rate than you deducted at.
Deferral isn't free, though — the IRS eventually collects through required minimum distributions, which can bunch into large taxable withdrawals later. That future tax bill is exactly what Roth conversions in low-income years aim to defuse. Tax-deferred, tax-free (Roth), and taxable accounts each behave differently, and holding a mix gives you levers to pull in retirement.
This definition is general information to help you understand a term, not financial, tax, or legal advice. Figures that change year to year (limits, thresholds, rates) should be confirmed against current official sources. For guidance on your situation, a licensed fee-only fiduciary is the right next step.