Liturgy, in our social sense, is a solemn Divine service, combined with the offering of the body and blood of the Lord, established by the Savior Himself, before His free passion, at the Last Supper. This was the first liturgy from the beginning of the world at which the Priestly Christ, as the Great Hierarch according to the order of Melchizedek (Ps. 109:4), offered to God the Father, under the guise of bread and wine, His body and blood, which, after that, he actually offered on the altar of the cross as a sacrifice for the sins of the world. Having communed His apostles with this body and blood, the Lord commanded them: to do this in remembrance of Him, that is, so that they, in remembrance of His suffering, and themselves, following His example, would perform this sacred act until the end of the ages, with the hope that, according to His saying: he who eats My body and drinks My blood abides in Me, and I in him (John 6:56), they, communicating with Him and becoming partakers of Him Divine nature, worthy to be partakers of His Kingdom!
The Liturgy contains the complete history, or the mysterious contemplation of the Lord Jesus Christ: first, Promised by God and prophesied by the prophets, then coming into the world for the sake of its salvation, and finally, having to come again in glory, in order to judge the living and the dead. From this it is clear that in the sacred rites of the liturgy, under the divine rites, all the actions of the great Sacrament of Redemption are presented to us, which is why it is also called Mystery, because through external actions it transfers the thoughts of the believer to the mysterious, spiritual meaning of its content.
Since apostolic times, the liturgy has consisted of three parts: Proskomedia, Liturgy of the Catechumens and Liturgy of the Faithful.