A religious priest belongs to a particular religious order. Each religious order is founded to fulfill a particular need in the Catholic Church through various ministries. “Order priests” can be assigned to any location and any ministry where their religious congregation is present.
A diocesan priest is one who is responsible primarily to the bishop of his particular diocese, a specific geographical region of the Church governed by the bishop. Within this region, the priest usually serves in a parish, though he may also be involved in other ministries like administration, communications, teaching and hospital or prison chaplaincy.
Both religious and diocesan priests perform sacramental ministry.