Most Catholics were taught two primary prayers to pray as a child. One was the Our Father and the other was the Hail Mary.
For this and other reasons, many of us consider the Our Father a prayer of private devotion.
However, the Catechism of the Catholic Church points out that the Lord's Prayer is also a liturgical prayer, designed to be prayed in public liturgy:
According to the apostolic tradition, the Lord's Prayer is essentially rooted in liturgical prayer: "[The Lord] teaches us to make prayer in common for all our brethren. For he did not say "my Father" who art in heaven, but "our" Father, offering petitions for the common body."
Our Father
This last point, which is a quote from St. John Chrysostom, helps illustrate the idea that Jesus designed the prayer to be prayed in common, praying, "Our Father."
Jesus was not teaching his disciples how to pray privately, but how to pray with others.
This isn't to say that the Our Father is not a prayer of private devotion, but that the prayer is most suited to the public liturgy.
The Catechism explains more specifically which types of liturgy that the Church uses the Our Father:
In all the liturgical traditions, the Lord's Prayer is an integral part of the major hours of the Divine Office. In the three sacraments of Christian initiation its ecclesial character is especially in evidence [Baptism, Confirmation, Eucharist].
Most Catholics are familiar with praying the Our Father during Mass on Sundays and during daily Masses:
In the Eucharistic liturgy the Lord's Prayer appears as the prayer of the whole Church and there reveals its full meaning and efficacy. Placed between the anaphora (the Eucharistic prayer) and the communion, the Lord's Prayer sums up on the one hand all the petitions and intercessions expressed in the movement of the epiclesis and, on the other, knocks at the door of the Banquet of the kingdom which sacramental communion anticipates.
The Lord's Prayer has also become a common prayer to be recited in gatherings of Christians of different denominations. The Our Father is a common heritage of all Christians, as it is a prayer that Jesus taught himself.
