It refers, essentially, to the Catholic concept of penance:
Catechism of the Catholic Church:
1459 Many sins wrong our neighbor. One must do what is possible in order to repair the harm (e.g., return stolen goods, restore the reputation of someone slandered, pay compensation for injuries). Simple justice requires as much. But sin also injures and weakens the sinner himself, as well as his relationships with God and neighbor. Absolution takes away sin, but it does not remedy all the disorders sin has caused. Raised up from sin, the sinner must still recover his full spiritual health by doing something more to make amends for the sin: he must "make satisfaction for" or "expiate" his sins. This satisfaction is also called "penance."
Q. 800. Why does the priest give us a penance after Confession?
A. The priest gives us a penance after Confession, that we may satisfy God for the temporal punishment due to our sins.
Q. 801. Why should we have to satisfy for our sins if Christ has fully satisfied for them?
A. Christ has fully satisfied for our sins and after our baptism we were free from all guilt and had no satisfaction to make. But when we willfully sinned after baptism, it is but just that we should be obliged to make some satisfaction.
*Q. 804. Why does God require a temporal punishment as a satisfaction for sin?
A. God requires a temporal punishment as a satisfaction for sin to teach us the great evil of sin and to prevent us from falling again.
Q. 805. Which are the chief means by which we satisfy God for the temporal punishment due to sin?
A. The chief means by which we satisfy God for the temporal punishment due to sin are: Prayer, Fasting, Almsgiving; all spiritual and corporal works of mercy, and the patient suffering of the ills of life.