We are taught in Scripture to pray always, and we see that Christ Himself set aside particular times to pray.
‘Indeed, nothing is to be preferred to the work of God.’ – The Rule of Saint Benedict 43.3
Following the practice of the Jewish people, the apostles met to pray the Psalms at particular hours, and this was taken up by the early Church. Eventually this led to a set cycle of hours, or fixed times for praying the Psalms. This prayer, which is called the Liturgy of the Hours, or the Divine Office, is intended to overflow into the rest of daily life, enabling us to “consecrate to God the whole cycle of the day and the night” (General Instruction of the Liturgy of the Hours, 10). We pray at seven different hours of the day. ‘Seven times a day I praise you.’ Ps 119.164
The Church considers two of these hours, Lauds (Morning Prayer) and Vespers (Evening Prayer), to be the two “hinges” of the Liturgy of the Hours. Each hour has its own particular character ordered to the time of day; thus Lauds focuses on praise, while Vespers is chiefly a prayer of thanksgiving. We pray this prayer of the Church not for ourselves only, but for the entire Church and for all of humanity, united with all the faithful around the world. “In the liturgy of the hours, the Church, hearing God speaking to his people and recalling the mystery of salvation, praises him without ceasing by song and prayer and intercedes for the salvation of the whole world” (Code of Canon Law, 1173). The Church promotes the practice of inviting the faithful “to celebrate the principal hours in common, especially on Sundays and holy days” (GILH 23).
Father Timothy Gallagher talks about the Divine Office.
The orange booklets they mention in the video unfortunately are only available in the U.S.