There are a few different forms of the Sacrament of Reconciliation. The one we’re most accustomed to is individual confession (usually, in a confessional in a church).
However, another form – which is encountered most often at Advent and at Lent – is a communal penance service. In this service (which is not a ‘Mass’ – there’s no Liturgy of the Eucharist), there are prayers, readings, (sometimes) a homily, and perhaps a prayer that expresses our contrition. Then, there is the opportunity to go for individual confession (again, usually in a confessional) in order to receive sacramental absolution. Finally, there is a closing prayer and a dismissal (although, to tell the truth, this ‘ending’ rarely happens – Catholics are too accustomed to leaving church after individual confession, so they generally just leave after receiving absolution!).
So, this is just another form for the Sacrament of Reconciliation. The communal ‘service’ itself doesn’t take the place of individual confession, nor does it give sacramental absolution; that only happens in individual confession, which is generally offered in the context of the service.
Does that help?