"Monsignor" is a title granted to a Catholic priest in recognition of his outstanding service to the church. A monsignor enjoys a higher rank than an ordinary priest, but his function and authority do not change.
Beginning in the 14th century, priests employed by the pope were addressed as "my lord" or monsignor, in recognition of their service to the papacy.
A bishop who believes that a priest has performed exceptionally petitions the pope to grant the candidate the title of monsignor.
If the pope accedes to the bishop's request, the Vatican Secretariat of State will issue a formal document known as a diploma granting the priest the title and citing all he has done for the church.
Three Types of Monsignors
A "protonotary apostolic" is an honorary member of the Roman Curia, the administrative heart of the church. A "prelate of honour to his holiness" is an honorary member of the pope's court. A "chaplain to his holiness" is an honorary member of the clergy who staff the pope's chapels.
Monsignors wear a black cassock with red or fuchsia buttons and piping, a fuchsia sash and, on ceremonial occasions, a fuchsia cape.