Most Christians interpret the parable of the prodigal son as an illustration of God's willingness to forgive those who admit their mistakes and show humility. Jesus expresses the parable in a way that contrasts God's positive attitude with the critical attitude of some religious leaders.
The parable begins by introducing the prodigal son, who is requesting his inheritance from his father. In Jesus' time, doing this before the father's death was considered disrespectful. Even so, the father decides to grant the request so the son can leave home. The prodigal son decides to spend the inheritance on frivolous matters. As a result, he becomes poor and struggles to survive. Christians see this introduction as a representation of God's willingness to let people make their own decisions, even if they lead to painful consequences.
The prodigal son admits that he is wrong to leave his father and makes the decision to return. The son believes he must earn his way back into the household and offers to become the father's servant. The father ignores the offer and accepts the son back joyously. Christians see this part as a representation of God's happiness upon witnessing the repentance of a sinner, as well as the extent of God's forgiveness. The older brother is unhappy when the prodigal son is pardoned. Jesus uses this character to show the Pharisees their error in condemning sinners without compassion.