The Liturgy of the Hours, also known as the Divine Office or the Work of God (Opus Dei), is the daily prayer of the Church, marking the hours of each day and sanctifying the day with prayer.The Hours are a meditative dialogue on the mystery of Christ, using scripture and prayer.At times the dialogue is between the Church or individual soul and God; at times it is a dialogue among the members of the Church; and at times it is even between the Church and the world.The Divine Office "is truly the voice of the Bride herself addressed to her Bridegroom. It is the very prayer which Christ himself together with his Body addresses to the Father." (SC 84)The dialogue is always held, however, in the presence of God and using the words and wisdom of God.Each of the five canonical Hours includes selections from the Psalms that culminate in a scriptural proclamation.The two most important or hinge Hours are Morning and Evening Prayer. These each include a Gospel canticle:the Canticle of Zechariah from Luke 1:68-79 for Morning Prayer (known as the Benedictus), and the Canticle of Mary from Luke 1:46-55 for Evening Prayer (known as the Magnificat). The Gospel canticle acts as a kind of meditative extension of the scriptural proclamation in light of the Christ event.Morning and Evening Prayer also include intercessions that flow from the scriptural proclamation just as the Psalms prepare for it.
"The hymns and litanies of the Liturgy of the Hours integrate the prayer of the psalms into the age of the Church, expressing the symbolism of the time of day, the liturgical season, or the feast being celebrated. Moreover, the reading from the Word of God at each Hour (with the subsequent responses or troparia) and readings from the Fathers and spiritual masters at certain Hours, reveal more deeply the meaning of the mystery being celebrated, assist in understanding the psalms, and prepare for silent prayer." (CCC 1177)
The five Hours of the Divine Office are:
Office of Readings
"The office of readings seeks to provide God's people, and in particular those consecrated to God in a special way, with a wider selection of passages from sacred Scripture for meditation, together with the finest excerpts from spiritual writers. Even though the cycle of scriptural readings at daily Mass is now richer, the treasures of revelation and tradition to be found in the office of readings will also contribute greatly to the spiritual life" (General Instruction of the Liturgy of the Hours [GILH], no. 55).
Morning Prayer
"As is clear from many of the elements that make it up, morning prayer is intended and arranged to sanctify the morning. St. Basil the Great gives an excellent description of this character in these words: "It is said in the morning in order that the first stirrings of our mind and will may be consecrated to God and that we may take nothing in hand until we have been gladdened by the thought of God, as it is written: 'I was mindful of God and was glad' (Ps 77:4 [Jerome's translation from Hebrew]), or set our bodies to any task before we do what has been said: 'I will pray to you, Lord, you will hear my voice in the morning; I will stand before you in the morning and gaze on you' (Ps 5:4-5)."
"Celebrated as it is as the light of a new day is dawning, this hour also recalls the resurrection of the Lord Jesus, the true light enlightening all people (see Jn 1:9) and "the sun of justice" (Mal 4:2), "rising from on high" (Lk 1:78). Hence, we can well understand the advice of St. Cyprian: "There should be prayer in the morning so that the resurrection of the Lord may thus be celebrated" (GILH, no. 38).
Daytime Prayer (can be prayed at Midmorning, Midday, or Midafternoon)
"Following a very ancient tradition Christians have made a practice of praying out of private devotion at various times of the day, even in the course of their work, in imitation of the Church in apostolic times. In different ways with the passage of time this tradition has taken the form of a liturgical celebration.
"Liturgical custom in both East and West has retained midmorning, midday, and midafternoon prayer, mainly because these hours were linked to a commemoration of the events of the Lord's passion and of the first preaching of the Gospel" (GILH, no. 74-75).
Evening Prayer
"When evening approaches and the day is already far spent, evening prayer is celebrated in order that 'we may give thanks for what has been given us, or what we have done well, during the day.' We also recall the redemption through the prayer we send up 'like incense in the Lord's sight,' and in which 'the raising up of our hands' becomes 'an evening sacrifice' (see Ps 141:2). This sacrifice 'may also be interpreted more spiritually as the true evening sacrifice that our Savior the Lord entrusted to the apostles at supper on the evening when he instituted the sacred mysteries of the Church or of the evening sacrifice of the next day, the sacrifice, that is, which, raising his hands, he offered to the Father at the end of the ages for the salvation of the whole world.' Again, in order to fix our hope on the light that knows no setting, 'we pray and make petition for the light to come down on us anew; we implore the coming of Christ who will bring the grace of eternal light.' Finally, at this hour we join with the Churches of the East in calling upon the 'joy-giving light of that holy glory, born of the immortal, heavenly Father, the holy and blessed Jesus Christ; now that we have come to the setting of the sun and have seen the evening star, we sing in praise of God, Father, Son, and Holy Spirit…'" (GILH, no. 39).
https://www.usccb.org/prayer-and-worship/liturgy-of-the-hours