Called many different names, including the perpetual wealth code, cashflow banking, and the money multiplier, infinite banking involves borrowing against yourself using a participating whole life insurance policy.
To go more in-depth, whole life insurance has a cash surrender value, AKA a cash value. This value is the amount of money that the insurance company makes available to you if you cancel the policy. With participating whole life insurance policies, your cash value goes up every time the company pays dividends.
Your bank basically consists of the premium payments by you + the dividends paid by the life insurance company + the guaranteed interest rate. As a policy owner, you can borrow against yourself and become your very own bank.