Liturgia enim, per quam, maxime in divino Eucharistiae Sacrificio, “opus nostrae Redemptionis exercetur”(1), summe eo confert ut fideles vivendo exprimant et aliis manifestent mysterium Christi et genuinam verae Ecclesiae naturam, cuius proprium est esse humanam simul ac divinam, visibilem invisibilibus praeditam, actione ferventem et contemplationi vacantem, in mundo praesentem et tamen peregrinam; et ita quidem ut in ea quod humanum est ordinetur ad divinum eique subordinetur, quod visibile ad invisibile, quod actionis ad contemplationem, et quod praesens ad futuram civitatem quam inquirimus(2). Unde, cum Liturgia eos qui intus sunt cotidie aedificet in templum sanctum in Domino, in habitaculum Dei in Spiritu(3), usque ad mensuram aetatis plenitudinis Christi(4), miro modo simul vires eorum ad praedicandum Christum roborat, et sic Ecclesiam iis qui sunt foris ostendit ut signum levatum in nationes(5), sub quo filii Dei dispersi congregentur in unum(6) quousque unum ovile fiat et unus pastor(7).
Vatican Website Translation:
For the liturgy, “through which the work of our redemption is accomplished,”  most of all in the divine sacrifice of the Eucharist, is the outstanding means whereby the faithful may express in their lives, and manifest to others, the mystery of Christ and the real nature of the true Church. It is of the essence of the Church that she be both human and divine, visible and yet invisibly equipped, eager to act and yet intent on contemplation, present in this world and yet not at home in it; and she is all these things in such wise that in her the human is directed and subordinated to the divine, the visible likewise to the invisible, action to contemplation, and this present world to that city yet to come, which we seek . While the liturgy daily builds up those who are within into a holy temple of the Lord, into a dwelling place for God in the Spirit , to the mature measure of the fullness of Christ , at the same time it marvelously strengthens their power to preach Christ, and thus shows forth the Church to those who are outside as a sign lifted up among the nations  under which the scattered children of God may be gathered together , until there is one sheepfold and one shepherd .
Slavishly Literal Translation:
For the Liturgy, through which, especially in the divine sacrifice of the Eucharist “the work of our Redemption is accomplished” [Secret of the Ninth Sunday after Pentecost in the Missale Romanum in use at the time of the Council], makes it possible in the highest degree for the faithful to express by living and to manifest to others the mystery of Christ and the genuine nature of the true Church, to which it is proper to be simultaneously human and divine, visible and endowed with invisible things, fervent in action and intent on contemplation, present in the world and nevertheless a pilgrim; and indeed in such a way that in it that which is human is ordered and subordinated to the divine, that which is of action to contemplation, and that which is present to the city to come which we seek [cf. Hebrews 13:14]. Whence, while the Liturgy daily builds up those who are within into a holy temple in the Lord, into an abode of God in the Spirit [cf. Ephesians 2:21-22], unto the measure of the age of the fullness of Christ [cf. Ephesians 4:13], in a wondrous way it simultaneously strengthens people for their proclaiming Christ, and so it displays the Church to those who are outside it as a sign lifted unto the nations [cf. Isaiah 11:12], under which the scattered children of God may be gathered into one [cf. John 11:52], until there is one sheepfold and one shepherd [John 10:16].
I do not think that the importance of this article for interpreting the subsequent conciliar discussions as well as for the implementation of the liturgical reforms can be overestimated. The document declares the intimate connection between liturgy and ecclesiology.
I would call our attention to at least the following topics raised in the article:
1) The liturgy (laos + ergon) is action/work (God’s work conjoined to the Church’s work on behalf of humanity in Christ): divine and human activity [theandric] by which redemption takes place.
2) The liturgy, while finding its deepest expression in the celebration of the Eucharist, comprises more than the Mass.
3) The liturgy is the premiere (but not the only) means by which the faithful may “express by living” and “display to others” two supernatural realities: a) the mystery of Christ (and we could spend much time reflecting on the recovery of “Mystical Body” theology as well as Odo Casel’s “theology of the mysteries” as background to this declaration) and b) the “genuine nature of the true Church” (and we could spend much time reflecting on the enrichment of Bellarmine’s juridical notion of the Church as “perfect society” by this notion of the Church arising from the liturgy/Eucharist).
4) Like the liturgy, the Church manifests itself in the nature of a sacrament, the visible/material elements both manifesting/giving access to and concealing/pointing beyond themselves to the invisible/spiritual.
5) Connecting the liturgy to the goals of the council articulated in the previous article, the text declares that the liturgy (considered ad intra) deepens the spiritual life of the faithful and equips them for evangelical mission while (considered ad extra) it manifests in sign the nature of the Church to “the scattered children of God” as an invitation for unity.
6) Finally, I think the footnotes are interesting: one citation taken from a liturgical text and six allusions to biblical texts. Is it significant that, at least at this stage, there is little citation of other sources?