Is it some sort of general confession? Is it something I could or should go to and watch? Or is it simply there are a bunch of people and priests and the priests hear individual confessions, only it’s like a marathon?
The Rite of Penance describes “Penitential Services” in n. 36 - 37. It has examples of them in Appendix II. It does not includes the sacrament of reconciliation, (also called the “sacrament of penance” or the “sacament of confession”). The correct title for what is described above in post #4 is “Rite of Reconciliation of Several Penitents with Individual Confession and Absolution”. It could be that someone has chosen the term “Penance Service” for this.
But a “Penitential Service” is a “Celebration of the Word of God” which does not require a priest. As described in the Rite of Penance:
“V. PENITENTIAL SERVICES
NATURE AND STRUCTURE
36. Penitential services are gatherings of the people of God to hear God’s word as an invitation to conversion and renewal of life and as the message of our liberation from sin through Christ’s death and resurrection. The structure of these services is the same as that usually followed in celebrations of the word of God [footnote 51: See Sacred Congregation for Rites, Instruction *Inter Oecumenici, September 26, 1964, nos. 37-39] and given in the
Rite for Reconciliation of Several Penitents.
It is appropriate, therefore, that after the introductory rites (song, greeting, and opening prayer) one or more biblical readings be chosen with songs, psalms, or periods of silence inserted between them. In the homily these readings should be explained and applied to the congregation. Before or after the readings from Scripture, readings from the Fathers or other writers may also be selected that will help the community and each person to a true awareness of sin and heartfelt sorrow, in other words, to bring about conversion of life.
After the homily and reflection on God’s word, it is desireable that the congregation, united in voice and spirit, pray together in a litany or in some other way suited to general participation. At the end the Lord’s Prayer is said, asking God our Father “to forgive us our sins as we forgive those who sin against us … and deliver us from evil.” The priest or minister who presides concludes with a prayer and the dismissal of the people.
BENEFIT AND IMPORTANCE
37. Care must be taken to ensure that the faithful do not confuse these celebrations with the celebration of the sacrament of penance. …”
(The Rites Volume One, Liturgical Press, 1990, ISBN: 0-8146-6015-0, page 541-542).
Appendix II has numerous examples, with the following headings:
I Penitential Celebrations During Lent
First example
Second example
II Penitential Celebrations During Advent
III Common Penitential Celebrations
i Sin and Conversion
ii The Son Returns to the Father
iii The Beatitudes
iv For Children
v. For Young People
vi. For the Sick