The word Gospel simply means "good news". The central message of the Bible is The Gospel, or good news, about the person and work of Jesus Christ. In 1 Corinthians 15:1-4, the Apostle Paul provides the most concise summary of the Gospel: the man Jesus is also God, He died on a cross in our place paying the penalty for our sins; three days later He rose to conquer sin and death and give the gift of salvation to all who believe in Him alone for eternal life.
The great reformer Martin Luther rightly said that, as sinners, we are prone to pursue a relationship with God in one of two ways. The first is Religion/spirituality and the second is the Gospel. The two are antithetical in every way.
Religion says that if we obey God He will love us.
The Gospel says that it is because God has loved us through Jesus that we can obey.
Religion says that the world is filled with good people and bad people.
The Gospel says that the world is filled with bad people who are either repentant or unrepentant.
Religion says that you should trust in what you do as a good moral person.
The Gospel says that you should trust in the perfectly sinless life of Jesus because He alone is the only good and truly moral person who will ever live.
The goal of Religion is to get from God such things as health, wealth, insight, power, and control.
The goal of The Gospel is not the gifts God gives, but rather God as the gift given to us by grace.
Religion is about what I have to do to be forgiven and be at peace with God.
The Gospel is about what Jesus did to provide for my forgiveness and make peace with God for me.
Religion is about what I have to do to remain "saved".
The Gospel is about what Jesus has already done to secure my salvation.
Religion sees hardship in life as punishment from God.
The Gospel sees hardship in life as a type of discipline that reminds us of Jesus' sufferings and is used by God in love to help us identify and become more like Jesus.
Religion is about me.
The Gospel is about Jesus.
Religion leads to an uncertainty about my standing before God because I never know if I have done enough to please God.
The Gospel leads to a certainty about my standing before God because of the finished work of Jesus on my behalf on the cross.
Religion ends in either pride (because I think I am better than other people) or despair (because I continually fall short of God's commands).
The Gospel ends in humble and confident joy because of the power of Jesus at work for me, in me, through me, and sometimes in spite of me.