The Catechism of the Catholic Church, #1174, says, “The mystery of Christ, His Incarnation and Passover, which we celebrate in the Eucharist especially at the Sunday assembly, permeates and transfigures the time of each day, through the celebration of the Liturgy of the Hours, ‘the divine office.’ This celebration, faithful to the apostolic exhortations to ‘pray constantly,’ is ‘so devised that the whole course of the day and night is made holy by the praise of God.’ In this ‘public prayer of the Church,’ the faithful (clergy, religious, and lay people) exercise the royal priesthood of the baptized. Celebrated in ‘the form approved’ by the Church, the Liturgy of the Hours ‘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.'”
For more details, see the Catechism of the Catholic Church, starting at #1174.