As its name implies, singe premium whole life insurance is a form of whole life insurance which can be paid for using a single, large premium. The premium paid normally matches the face value of the policy, so the cash value matches the face value from the beginning.
Your equity in the life insurance policy normally earns interest, and you may receive dividends if the insurance company performs well.
Single premium whole life insurance policies are normally used as an investment instrument (much like an interest-earning savings account). Building the full amount of cash value from the beginning is financially advantageous over building cash value over a long period because you earn interest on the full amount right from the start.
Life insurance comparison