[The following is a bare-bones explanation of what happens during the Latin Mass. It does not even begin to describe the rich symbolism behind all the liturgical actions...]
The Mass begins with the Priest and Servers entering. They stand at the entrance to the Sanctuary at the foot of the stairs to the altar and engage in a dialogue of unworthiness to enter this Holy place.
Introibo ad altare Dei
Ad Deum qui laetificat juventutem meam.
I shall go to the altar of God
To God, the joy of my youth.
The priest then confesses his sinfulness, and the servers pray on behalf of the congregation that God will forgive him his sins.
I confess to Almighty God, to Blessed Mary Ever Virgin, to Blessed Michael the Archangel, to Blessed John the Baptist, to the Holy Apostles Peter and Paul, to all the saints, and to you, brothers, that I have sinned exceedingly in thought, word, deed: through my fault, through my fault, through my most grievous fault, and I ask Blessed Mary Ever Virgin, Blessed Michael the Archangel, Blessed John the Baptist, the Holy Apostles Peter and Paul, all the Saints, and you brothers, to pray for me to the Lord our God.
The servers then confess their sinfulness on behalf of the congregation in the same terms as the priest, but separately, and the priest prays for their forgiveness.
After a short further dialogue, the priest approaches the altar and kisses it. From this point on, the priest will not leave the altar for the entire Mass except to give his sermon. Throughout the Mass, the priest is largely standing in front of the altar facing God with his back to the people, while the servers kneel on the stairs leading up to the altar.
The priest then recites the Kyrie Eleison (the Lord have mercy) with the servers, or the choir may sing it.
The Gloria is then recited by the priest or sung by the choir following which the priest prays the Collect for the day.
The priest then reads the Epistle of the day on the right hand side of the altar (still facing the altar not the people). There is only one reading other than the Gospel and it is always from the New Testament.
After the Epistle, the Gradual is read (the Alleluia). While the server takes the Missal from the right-hand side of the altar to the left, the priest prays a beautiful prayer that he will be worthy to proclaim the gospel:
Cleanse my heart and my lips, O Almighty God, who cleansed the lips of the Prophet Isaias with a burning coal, in Your gracious mercy deign so to purify me that I may worthily proclaim Your holy Gospel. Through Christ our Lord. Amen. The Lord be in my heart and on my lips that I may worthily proclaim His holy Gospel.
The Gospel is then read. Followed by the sermon. The priest will often read the Epistle and the Gospel in English before his sermon. The Creed then follows.
A long Offertory prayer then follows, which begins:
Accept, O Holy Father, Almighty and Eternal God, this spotless host, which I, your unworthy servant, offer to You, my living and true God, to atone for my numberless sins, offences and negligences; on behalf of all here present and likewise for all faithful Christians living and dead, that it may profit me and them as a means of salvation to life everlasting. Amen.
Then the washing of his hands:
I wash my hands in innocence; and I go around Your altar, O Lord, giving voice to my thanks, and recounting all Your wondrous deeds. O Lord, I love the house in which You dwell, the tenting place of Your glory. Gather not my sould with those of sinners, nor with men of blood my life. On their hands are crimes, and their right hands are full of bribes. But I walk in integrity; redeem me, and have pity on me. My foot stands on level ground; in the assemblies I will bless you, O Lord.
Accept, most Holy Trinity, this offering which we are making to You in remembrance of the passion, resurrection and ascension of Jesus Christ, Our Lord; and in honour of blessed Mary ever Virgin, Blessed John the Baptist, the Holy Apostles Peter and Paul, and of [the Saint whose relics are in the altar] and of all the Saints; that it may add to their honour and aid our salvation; and may they deign to intercede in heaven for us who honour their memory here on earth.
Only then does he invite the servers to pray on behalf of the congregation that the sacrifice will be pleasing to God.
There follows the Secret prayer of the day, which the priest recites inaudibly, and the Preface, followed by the Sanctus:
Sanctus, Sanctus, Sanctus, Dominus Deus Sabaoth. Pleni sunt coeli et terra gloria tua. Hosanna in excelsis. Benedictus qui venit in nomine Domini. Hosanna in excelsis.
There then follows the Roman Canon, which the priest prays silently. The central part of the canon is the Consecration:
hoc est enim corpus meum
hic est enim calix sanguinis mei
After the consecration, the priest genuflects (the server holds the back of the priest's vestments while he does so) while the server rings a bell, he then elevates the Sacred Host (as the case may be) for adoration by the faithful while the server rings a bell, and then he genuflects a second time while the server rings the bell the third time. This is repeated for the Precious Blood.
The Canon is rich in the theology of the Mass, the re-presentation to God of the Sacrifice of Calvary, the unbloody sacrifice of the spotless victim:
Mindful, therefore, Lord, we, Your ministers, as also Your holy people, of the same Christ, Your Son, our Lord, remember His blessed passion, and also His Resurrection from the dead, and finally His glorious Ascension into heaven, offer to Your supreme Majesty, of the gifts bestowed upon us, the pure Victim, the holy Victim, the all-perfect Victim: the holy Bread of life eternal and the Chalice of perpetual salvation.
The entire canon is recited in silence, except for the words "nobis quoque peccatoribus" ("To us sinners also...").
Immediately following the Doxology, the priest recites the Pater Noster (the Our Father) and prays a beautiful prayer calling for God's forgiveness and the intercession of the Blessed Virgin, the Apostles Peter, Paul and Andrew and all the Saints.
The priest then places a piece of the host in the chalice and recites the Agnus Dei (Lamb of God).
Then there is a separate communion rite for the priest before the communion of the faithful. The priest recites his own "Domine non sum dignus" (Lord, I am not worthy) and takes communion. The priest then turns to the people holding up the host saying "Ecce Agnus Dei" (Behold the Lamb of God) and recites a separate "Domine non sum dignus" for the people.
The faithful then proceed to communion. Communion is received on the tongue kneeling at the altar rails. The priest says:
Corpus Domini nostri Jesu Christi custodiat animam tuam in vitam aeternam. Amen.
May the Body of our Lord Jesus Christ preserve your soul unto everlasting life. Amen
After communion, there are the ablutions where the priest cleanses the Sacred Vessels, the Postcommunion prayer of the day, and finally the Final Prayer and Dismissal "Ite missa est" (Go, you are sent forth).
The priest then goes to the Gospel side of the altar and recites the "Last Gospel", the beginning of St John's Gospel ("In the beginning was the Word..."). This is read at every Mass.
Following this, in a low Mass, the priest and the faithful recite the Hail Mary, the Hail Holy Queen and the Prayer to St Michael Archangel together.