The balance in your annuity as of the date you establish annuitization. The more money in your account, the more you can receive each month. Obviously, the longer the payment schedule, the less you get with each payment. The rate of return the insurance company assumes it will earn during your payout period. The higher return it expects to earn, the more money you get every payment.
Most annuities offer seven or more annuitization choices.
You get a monthly check for life. Only when you die does the money stop. I rarely recommend this choice, because payments stop when you die, which could be tomorrow if that bus hits you. Your spouse and children get nothing, even if you lived long enough to receive only one payment from your annuity. If the insurance company estimates that you'll live 20 years and you live 30, the company will send you more than your account balance justifies.