The Catholic Sacrament of Reconciliation (also known as the Sacrament of Penance, or Penance and Confession) has three elements: Conversion, Confession, and Celebration. In it, we find God's unconditional forgiveness, and as a result, we are called to forgive others. Children typically prepare for First Reconciliation and First Eucharist at the same time; learn about Sacrament Preparation here. Adult Catholics who have been baptized but celebrated no other sacraments can prepare through Christian Initiation of Adults; info here.
Examination of Conscience before Reconciliation:
https://sjbalameda.org/examination-of-conscience-reconciliation