Two broad types: immediate annuities (pay-outs start within a year of purchase) and deferred annuities (accumulation phase before pay-out). Subtypes include fixed (guaranteed return), variable (returns tied to underlying investments) and indexed (linked to a market index with caps and floors).
Annuities trade flexibility for longevity protection: you cannot outlive a life annuity, but you also cannot reclaim the principal once annuitised. Best for retirees worried about longevity risk; less attractive when fees are high or interest rates low.
A 65-year-old uses CHF 500,000 to buy an immediate life annuity paying CHF 2,400/month for life; total payments depend on how long they live.