The Sacred Liturgy, nos. 25-28

25. "Full, Conscious, and Active Participation"
One of the most important principles that guided the liturgical reforms of the Second Vatican Council is that the faithful gathered for worship should exercise "full, conscious, and active participation" in the liturgy." This phrase has become a rallying cry for a variety of liturgical novelties and reforms. It is good to for all Catholics to understand precisely what it means.
The notion of "full, conscious, active participation" did not originate with Vatican II but with Pope Pius X, in the early years of the 20th Century. The fundamental meaning of the phrase is that all the faithful ought to understand the liturgy we celebrate, and dispose themselves properly to celebrate the sacred mysteries. Our interior attitude and understanding is of more importance than words and actions, although these are critical too, since they express our devotion.
Everyone has a role to play in the liturgy, according to his or her status in the Church: bishop, priest, deacon, lector, server, musician, or member of the congregation. These roles are distinct and should not be confused. It is the duty of every Catholic to study and come to understand the liturgy so that all may celebrate it with understanding and devotion.
RS, Ad Limina of JP II October 9, 1998

26. "Full, Conscious, and Active Participation"
The Ad Limina Address of Pope John Paul II on October 9, 1998 helps to clarify precisely what "full, conscious, and active participation" in the liturgy means.
Full participation means that every member of the assembly has a part to play in the liturgy, yet this does not mean that everyone does everything. The liturgy is "hierarchical and polyphonic." There are many roles and each one has its proper place. The roles of clergy and laity are distinct and cannot be interchanged.
Active participation means that the faithful participate in word, song, and gestures, yet they also actively participate in silence and attentive listening. Listening may appear passive but is actually an active element of the liturgy, whereby our minds are raised to heavenly realities when we listen to the readings or music sung by the Choir.
Conscious participation means that all the faithful ought to be instructed in the mysteries of the liturgy, so they are aware of what is happening. This includes Latin and Gregorian chant. This does not mean that the liturgy itself should constantly involve interruptions for instruction. At appropriate times, all ought to be introduced to the deep meaning of the mysteries we celebrate.
Ad Limina of JP II October 9, 1998

27. "Full, Conscious, and Active Participation"
"The celebration of the Mass, as the action of Christ and of the Church, is the center of the whole Christian life for the universal as well as the particular Church [i.e. "diocese"], and also for the individual faithful, who are involved "in differing ways according to the diversity of orders, ministries, and active participation."
"…the participation of the lay faithful too in the in the Eucharist and in the other celebrations of the Church’s rites cannot be equated with mere presence, and still less with a passive one, but is rather to be regarded as a true exercise of faith and of the baptismal dignity."
"…it does not follow that everyone must necessarily have something concrete to do beyond the actions and gestures [proscribed by the liturgical books]."
"Nor is the Eucharistic Sacrifice to be considered a ‘concelebration,’ in the univocal sense, of the Priest along with the people who are present…The community that gathers for the celebration of the Eucharist absolutely requires an ordained Priest…."
Accordingly, such terms as "celebrating community" or "celebrating assembly" are not to be used in this way, as if to say that the community offers the Eucharist, for this requires a priest.
RS 36-42

28. The Orans Position in the Liturgy
The role of the priest in the Liturgy is to act in persona Christi capitis, "in the person of Christ the Head" of the Body, the Church. The priest also stands before the Altar of God as a representative of the people, bringing their needs before God and begging His mercy and blessing on their behalf.
When interceding on behalf of the people in the Liturgy, the priest extends his hands. This position of prayer for the priest is called the Orans position, from the Latin orans, meaning "praying." It is a gesture common to most ancient religions. It is the natural human gesture of pleading with someone, "I beg you, help me." When focused heavenwards, it becomes an outward sign of supplicating God. It symbolizes the priest’s prayer on behalf of the people.
It is not a gesture proper to the Laity within the Liturgy (though in private prayer it is legitimate). Whenever private gestures of some people find their way into the Liturgy, the unity of the assembly is compromised, as is the rich system of symbols defined by the liturgical rubrics. The hierarchical nature of the Liturgy is also confused.
Extending hands during the Our Father is a gesture for the priests; and during the "For the kingdom, and the power, etc…" it is proscribed for the main celebrant alone, since he represents all. Extending hands is a liturgical gesture proper to the clergy, and not to the faithful, who have a distinct role of their own.