Yes, they are members of the three-fold order of the ordained ministry. The other two are bishop and priest. In all areas, the deacon assists the bishop and priest as needed and at their discretion. Specific roles in the liturgy traditionally include the reading of the Gospel and the dismissal. Deacons may also preach.
Deacons can perform all the sacramental roles of a priest except the consecration of bread and wine.
Deacons often play an important role in the teaching of the Church. The deacon's main role in the local church is to lead the Body of the Church into a deeper understanding of its diaconal ministry. Deacons are under Holy Orders to their bishop, and to other clergy to whom the bishop may assign them. They are not members of any parish or mission, but are canonically resident in a diocese. Those who feel they may have a vocation to this ministry must first talk with their priest.