A life insurance policy is a contract between you and an insurance company. In that contract, you agree to make payments (premiums) to the insurance company for a specified period of time (sometimes for the duration of your life), and the insurance company agrees to provide a lump-sum cash payout ("death benefit") in the event that you die within the duration of the policy. The contract is legally binding and government regulated.
A premium is the price you pay to the life insurance company to secure your coverage amount. It can be paid monthly, twice a year, or annually depending on your preference. If you continue to make premium payments, the insurance company must meet their obligation to provide your beneficiaries with the stated benefit in the event of your passing.
A beneficiary is a person (or persons) who will receive the proceeds of the life insurance policy when the insured person dies. You can name one person or multiple people as beneficiaries when you select a policy, but you will usually only have one primary beneficiary.
You are not locked into a life insurance policy, and can typically terminate it by ceasing to pay the premiums.