The mozzetta is a short elbow-length cape

Cape

Cape can be used to describe any sleeveless outer garment, such as a poncho, but usually it is a long garment that covers only the back half of the wearer, fastening around the neck. They were common in medieval Europe, especially when combined with a hood in the chaperon, and have had periodic...

 that covers the shoulders and is buttoned over the breast. It is worn over the rochet

Rochet

A rochet is a white vestment generally worn by a Roman Catholic or Anglican Bishop in choir dress. It is unknown in the Eastern Churches. The rochet is similar to a surplice, except that the sleeves are narrower...

 or cotta

Surplice

A surplice is a liturgical vestment of the Western Christian Church...

 as part of choir dress

Choir dress

Choir dress is the vesture of the clerics, seminarians and religious of traditional churches worn for public prayer, either apart from the eucharist or by those attending the eucharist as the clergy part of the congregation rather than as the celebrants...

 by some of the clergy

Clergy

Clergy is the generic term used to describe the formal religious leadership within a given religion. A clergyman, churchman or cleric is a member of the clergy, especially one who is a priest, preacher, pastor, or other religious professional....

 of the Catholic Church, among them the Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

, cardinals, bishop

Bishop (Catholic Church)

In the Catholic Church, a bishop is an ordained minister who holds the fullness of the sacrament of Holy Orders and is responsible for teaching the Catholic faith and ruling the Church....

s, abbot

Abbot

The word abbot, meaning father, is a title given to the head of a monastery in various traditions, including Christianity. The office may also be given as an honorary title to a clergyman who is not actually the head of a monastery...

s, canon

Canon (priest)

A canon is a priest or minister who is a member of certain bodies of the Christian clergy subject to an ecclesiastical rule ....

s and religious superiors. There used to be a small hood on the back of the mozzette of bishops and cardinals, but this was discontinued by Pope Paul VI

Pope Paul VI

Paul VI , born Giovanni Battista Enrico Antonio Maria Montini , reigned as Pope of the Catholic Church from 21 June 1963 until his death on 6 August 1978. Succeeding Pope John XXIII, who had convened the Second Vatican Council, he decided to continue it...

. The hood, however, was retained in the mozzette of certain canons and abbots, and also in the Popes'.
The colour of the mozzetta, which is always worn with a cassock

Cassock

The cassock, an item of clerical clothing, is an ankle-length robe worn by clerics of the Roman Catholic Church, Eastern Orthodox Church, Anglican Church, Lutheran Church and some ministers and ordained officers of Presbyterian and Reformed churches. Ankle-length garment is the meaning of the...

 and sometimes other choral vestments, represents the hierarchical rank of the person wearing it.