It’s a term to describe the legal right to recover when someone causes an accident which results in another person’s death.
The are written laws (called “statutes”) which strictly control wrongful death claims. Those laws specify who can make such a claim and limit what can be recovered. For example, if a single person without children dies and they have parents and siblings who survive, only the parents can recover no matter how close the siblings were.
These cases involve many technical and emotional issues. Your lawyer needs to be sensitive to these.