Both of these types of insurance protect you against injury caused in an automobile accident where the at-fault driver's liability car insurance coverage is inadequate. Though they're often lumped together, they're really two distinct policies.
Uninsured motorist insurance is needed when the other driver has no liability coverage.
Underinsured motorist coverage pays for the cost of your injuries that exceed the other driver's coverage maximum.
Most states require neither type of coverage, but some require one or the other, and a few even require both. They're more often required in no fault states.
The following are a few, but not all, of the insurance providers used by QuickQuoteUS