Annuities fall into four overlapping categories: immediate vs. deferred (when income starts), fixed vs. variable vs. indexed (how growth is calculated), single-premium vs. flexible-premium (how you fund it), and qualified vs. nonqualified (whether purchased inside a retirement account). Fixed annuities credit a guaranteed interest rate. Variable annuities invest in market-linked subaccounts. Fixed-indexed and Registered Index-Linked Annuities (RILAs) tie growth to a market index with a floor and a cap, offering partial market participation with limited downside.