Annuities are great tools for retirement planning, but they can be complicated, too. And the terminology can be confusing even when the underlying concept is simple. When it comes to this important piece of the retirement-security puzzle, how well do you understand annuities?

Here are 12 things we bet you didn't know about annuities.

2. While an annuity's growth is not taxed, your withdrawals and income payments will be.

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Annuity interest accumulates tax-deferred and is not taxed until it's withdrawn. With a deferred annuity, you decide when to withdraw interest and pay taxes on it. Interest credits and gains from all types of annuities are taxed as ordinary income, not long-term