The Catechism says:
1536 Holy Orders is the sacrament through which the mission entrusted by Christ to his apostles continues to be exercised in the Church until the end of time: thus it is the sacrament of apostolic ministry. It includes three degrees: episcopate, presbyterate, and diaconate.When a Bishop is ordained they receive the "fullness of the sacrament of Holy Orders". This means that they become "true and authentic teachers of the faith and have been made pontiffs and pastors." (CCC 1558) Priests and Deacons do not have all of this authority, but still share in the ministry of Christ and the sacrament of Holy Orders.
1538 Integration into one of these bodies in the Church was accomplished by a rite called ordinatio, a religious and liturgical act which was a consecration, a blessing or a sacrament. Today the word "ordination" is reserved for the sacramental act which integrates a man into the order of bishops, presbyters, or deacons, and goes beyond a simple election, designation, delegation, or institution by the community, for it confers a gift of the Holy Spirit that permits the exercise of a "sacred power" (sacra potestas)5 which can come only from Christ himself through his Church. Ordination is also called consecratio, for it is a setting apart and an investiture by Christ himself for his Church. The laying on of hands by the bishop, with the consecratory prayer, constitutes the visible sign of this ordination.
The diaconate is explained in this way:
1570 Deacons share in Christ's mission and grace in a special way. The sacrament of Holy Orders marks them with an imprint ("character") which cannot be removed and which configures them to Christ, who made himself the "deacon" or servant of all. Among other tasks, it is the task of deacons to assist the bishop and priests in the celebration of the divine mysteries, above all the Eucharist, in the distribution of Holy Communion, in assisting at and blessing marriages, in the proclamation of the Gospel and preaching, in presiding over funerals, and in dedicating themselves to the various ministries of charity.I hope this helps.