In insurance law, the administrator is generally a corporation hired to manage the insurance plan by collecting of contributions, assessing claims and distributing benefits.
In estate law, where a person dies intestate or without having named an executor, or having named an executor but who them died before the deceased, and where probate of the estate is necessary, the court needs to appoint a person to manage and wind-up the estate. This person - once appointed - is called an administrator.
The administrator who would then have power to deal with the debts and assets of a person who died.
Female administrators are called administratrix.
The term personal representative is used to describe a person who manages an estate and includes both administrators and executrix.
Some administrators are given limited powers because of the special circumstances such as administrators pendente lite. Others take on a partially administered estate, such as an administrator de bonis non.