For instance, if you buy a life insurance policy and pay your premiums. And, if you die while the life insurance plan is "In Force", the beneficiary your chose when starting your coverage will receive the death benefit stated in the life insurance policy.
The payout of the death benefit is subject to any exclusions in the life insurance policy.
Usually, if an individual is named beneficiary, that person would receive the proceeds from the life insurance plan free from any federal taxes.
The beneficiary may use the death benefit for any reason they choose, for instance, to pay for your burial, living expenses, pay off the mortgage, etc.
Life insurance is also used to help replace the income of the insured person so his/her family can go on living the lifestyle they enjoyed with the person who was insured.
Basically, life insurance is insurance (protection) on your life in case you die.
Here's how you can learn about term life insurance.