Every life insurance policy covers accidental death. Traditional life insurance policies provide full coverage (paying out proceeds in the event death occurs by illness or injury).
Policies that only cover accidental deaths are known as Accidental Death & Dismemberment life insurance programs. These policies typically feature much lower premiums than full coverage programs, but only pay out a death benefit if death occurs under certain conditions (e.g. a car accident or a plane crash – exact conditions vary by plan). If you only have an AD&D policy and you die due to something like a heart attack, the policy would not pay out any proceeds because that would be considered death due to illness.
Even though the premiums are less with AD&D policies, it can be worth paying the premiums for a full coverage life insurance policy to have that extra level of protection.