Holy Saturday is the final day of the Triduum and of Holy Week. It is a day of little liturgical activity, for example, there is no Mass. The sacrament of Reconciliation can be, and is usually, performed. It is a day on which we continue to reflect and meditate upon the death of Jesus and the implications that it has for us – our redemption. We continue, in a more devout and deeper way, our anticipation of the Resurrection of Jesus.
Liturgically, the Easter Vigil is part of Easter Sunday. A good reference as an overview for the Easter Vigil can be found at this link: https://www.catholicculture.org/culture/liturgicalyear/activities/view.cfm?id=1043