If one person performs a duty of another, they are then "equitable subrogated" to the rights of the person owed the duty. The most common form of subrogation is when an insurance company pays a claim caused by the negligence of another.
The act of putting by a transfer, a person in the place of another, or a thing in the place of another thing. It is the substitution of a new for an old creditor, and the succession to his rights, which is called subrogation; transfusio unius creditoris in alium. It is precisely the reverse of delegation.
There are three kinds of subrogation: 1. That made by the owner of a thing of his own free will; example, when be voluntarily assigns it. 2. That which arises in consequence of the law, even without the consent of the owner; example, when a man pays a debt which could not be properly called his own, but which nevertheless it was his interest to pay, or which he might have been compelled to pay for another, the law subrogates him to all the rights of the creditor. 3. That which arises by the act of law joined to the act of the debtor; as, when the debtor borrows money expressly to pay off his debt, and with the intention of substituting the lender in the place of the old creditor.