Gap Insurance

What Does Gap Insurance Mean?
A type of auto insurance that car owners can buy to protect themselves against losses that can arise when the amount of compensation received from a total loss does not fully cover the amount the insured owes on the vehicle's financing or lease agreement. This situation  arises when the balance owed on a car loan is greater than the book value of the vehicle.

Investopedia explains Gap Insurance
For example, according to the blue book, John's car is worth $15,000. However, he still owes a total of $20,000 worth of car payments. In the event that John's car is completely written off  as a result of an accident or theft, John's car insurance policy will reimburse him with $15,000. Because John owes the car financing company $20,000, however, he will still be $5,000 short, even though he no longer has a car.

If John had purchased gap insurance, the gap insurance policy would cover the $5,000 "gap", or the difference between the money received from reimbursement and the amount still owed on the car.