The one ordained ministry in the Catholic Church has three forms. It is constituted by the ministries of bishop, presbyter (priest), and deacon. These three dimensions of ministry have been a part of the order of the Church from early in the church’s history.
The Second Vatican Council emphasised an understanding that the ministry of the bishop has the “fullness of order”. The bishop’s ministry is articulated in the three dimensions of preaching, sanctifying and governing of the local Church (diocese). All bishops of the Catholic Church with the Pope represent the communion of the Church.
The other two forms of ordained ministry are related to the bishop’s ministry of unity and collaborate with the bishop in the service of the church and its mission. The presbyter and deacon find their identity in Jesus’ ministry, but are given their authority to serve through the bishop’s apostolic ministry.
The presbyter is usually the principal leader of a parish community, and participates in the priesthood of the bishop’s ministry grounded in Christ’s priesthood.
What has become known as the permanent Diaconate since Vatican II was a form of ministry that faded from the Church in the West for some centuries. However, Vatican II restored this form of the ordained ministry. The deacon participates in the service dimensions of the ministry, and grounds its spirituality in Christ the servant.
Inside a Roman Catholic parish, individuals help with church services. These people are known as "lay ministers." They volunteer within the church to help things run smoothly on Sundays and throughout the week. The cantor leads the singing. The lectors read Scripture. The Extraordinary Eucharistic Ministers help distribute communion during Mass and also take it to the housebound and ill. Altar servers assist the priest. Catechists teach the parish children about the Catholic faith.