A wrongful death claim usually stems from the victim's death from an accident and is brought on behalf of a relative or loved one.
For example, say someone is married with three children and becomes injured in a serious truck accident caused by the negligence of a trucker. If the victim is hospitalized and sues the person at fault, but before the victim's case is heard, they die from the injuries sustained in the truck wreck. The victim's spouse may proceed with the claim, after getting qualified as the personal representative of the estate, as a wrongful death matter against the person at fault.
You also need to be aware of the "survival statute" which preserves a victim's cause of action against an at-fault individual after the victim passes away from some cause other than the accident. This enables the estate to take over the victim's cause of action against the at-fault party. The damages available in a survival action include all the damages for the injury that are available to the actual victim if the individual survived.