What the Gospel is:
The Gospel is good news that is all about Jesus.
It begins with God creating man as good; in the image & likeness of God, and in relationship with God. Man (starting with the first man Adam, and continuing with us today) has sinned and rebelled against God, thus causing separation, enmity, and condemnation in our relationship with God.
The good news of the Gospel is that even though man rebelled against God, God the Father sent God the Son, who was physically born, lived a sinless and perfect life, then died on the cross where He absorbed the righteous wrath of God that all of mankind deserves. He in fact bore our sin (2 Corinthians 5:21a). Jesus was buried in a tomb and three days later rose again physically and bodily thus conquering Satan, sin and death.
Our redemption and new life comes by grace alone through faith alone in Christ alone (Ephesians 2:8-9). The way to reconciliation and right relationship with God was, is, and will always be through Jesus (Genesis 3:17, Ephesians 1:7-14, Romans 8:29-30).
What the Gospel is not:
Man-made religion or a list of do's and dont's.
There is a vast difference between religion and the Gospel, and here are a few examples:
Religion says, "I obey, therefore I'm accepted."
The Gospel proclaims, "I am accepted, therefore I obey."
Religion motivates through fear and insecurity.
The motivation of Gospel is based on grateful joy and gladness.
Religion calls us to obey God in order to get things from God.
The gift of the Gospel is God Himself. This gift brings about joyful obedience, delight and a desire to resemble our Father.
Religion bases identity and self-worth mainly on how hard I work or how moral I am. As a result there is disdain toward others who I deem to be lazy or immoral. This breeds a complex of superiority toward "outsiders".
The Gospel shows that my identity and self-worth are centered on Jesus, Who died for His enemies, and was excluded for me. I am saved by sheer grace, so I cannot look down on or feel superior to those who believe or practice something different than me. It is by grace that I am what I am. The Gospel is about declaring and demonstrating the love, light and truth about Jesus.
What the Gospel calls us to:
Faith, Repentance, & Worship - All in the context of Community.
Faith - The Gospel calls us to place our faith (deepest belief and trust of the heart) in the person and work of Jesus. It is this faith that admits and acknowledges that true life and relationship with God is through Jesus alone (John 14:6, Romans 6:23).
Repentance - The Gospel calls us to repent of sin. Sin is not just "disobeying the rules" but goes deeper to the motivation of what we do and do not do. This includes doing wrong things, but also doing right things for the wrong reasons. Jesus came preaching a message of repentance (Matthew 4:17) that continued to show that the God of the Bible is not simply concerned with moral performance, but with the motivation of the heart (Psalm 51:16-17).
Worship - The Gospel calls us to worship. All of life is worship and we are constantly worshipping (serving) someone or something (The Bible uses the language of "idols"). We sin when worship is directed toward things that are created rather than the Creator. In the new life that Jesus creates through the Gospel, we seek to smash our idols by the grace of God. In turn our lives are transformed into acts of worship to God's glory (Romans 12:1-2).
Community** - The Gospel calls us to live this new life in the context of a living community. As image bearers of God, we have been created for community. What sin has broken, Jesus has reconciled through the cross. Apart from Jesus' death and resurrection, true community is not possible. Through Jesus we have been reconciled to God and one another for the purpose of making an appeal to the world to be likewise reconciled (Romans 5:10, 2 Corinthians 5:17-20). The existence of a loving, Gospel-saturated community is a testimony to the truth of the Gospel.
*Much of this content is adapted from Timothy Keller's "Gospel in Life Study Guide" (pg 16)
**Portions of this paragraph were adapted from Brad House's book "Community"