The double indemnity rider is a accidental death clause that provides additional death benefit if you die resulting from accident.
In general, people are more likely to die from an illness rather than an accident.
And, there are some age and time limit restrictions on an accidental death clause, such as, you must die before age 65 or 70, and the death from an accidental must occur within a certain time period of the accident, for instance, 90 days or 1 year.
However, if you have the double indemnity rider on your $100,000 life insurance policy, and you die from a covered accident, your death benefit payment to your beneficiary would be $200,000.