A more thorough explanation:

A real party in interest is the person or entity who has the legal right to bring a lawsuit, even if someone else will ultimately benefit from the outcome of the case. This means that the real party in interest is the one who has a direct stake in the outcome of the case.

For example, in a wrongful death case, the real parties in interest are usually the surviving family members of the deceased person. Even though the damages awarded in the case will go to the deceased person's estate, the family members have the right to bring the lawsuit because they are the ones who have suffered a direct loss.

In the context of a trust, the real party in interest is usually the trustee. If someone damages a building owned by the trust, the trustee has the right to bring a lawsuit to recover damages, even though the beneficiaries of the trust will ultimately benefit from the outcome of the case.

It's important to note that many jurisdictions require that a lawsuit be brought in the name of the real party in interest. This means that the person or entity who has the legal right to bring the lawsuit must be the one named as the plaintiff in the case.

For example, in California, the law states that "every action must be prosecuted in the name of the real party in interest, except as otherwise provided by statute." This means that if someone wants to bring a lawsuit in California, they must be the real party in interest and must be named as the plaintiff in the case.