Repentance means a sincere turning away from sin and turn to God. A person must repent to receive eternal life in heaven, but this act does not earn salvation.
Ezekiel 18:30:
"Therefore,O house of Israel, I will judge you, each one according to his ways, declares the Sovereign LORD. Repent! Turn away from all your offenses; then sin will not be your downfall." (NIV)
Jesus also calls for repentance:
"The time has come," Jesus said. "The kingdom of God is near. Repent and believe the good news!" (Mark 1:15, NIV)
Repentance is an essential part of salvation, requiring a turning away from the sin-ruled life to a life characterized by obedience to God. The Holy Spirit leads a person to repent, but repentance itself cannot be seen as a "good work" that adds to our salvation.
The Bible states that people are saved by faith alone (Ephesians 2:8-9). However, there can be no faith in Christ without repentance and no repentance without faith. The two are inseparable.