Penance and Reconciliation (Confession)
You are sorry for your sins, you tell them to the priest, and God forgives you through him. Then you do the penance the priest gives you.
The sign
The words the priest says to forgive you in God’s name: the absolution.
Who gives it
The priest. He can never tell anyone what he heard in confession.
How many times
Many times. Serious sins must be confessed at least once a year.
What the Bible says
John 20:22-23
22When he had said this, he breathed on them; and he said to them: Receive ye the Holy Ghost. 23Whose sins you shall forgive, they are forgiven them; and whose sins you shall retain, they are retained.
Douay-Rheims Bible (Challoner revision), public domain.
Source: Catechism 1422-1424, 1449, 1457-1458, 1461, 1467, and 1491