Gospel
In the Greek, "gospel" simply means good news. It could have been good news about anything. In the Septuagint, the original Greek translation of the Hebrew Scriptures, the word group occurs approximately 29 times. The general meaning of the word, in that context, continues to mean good news, the good news that God is paying attention to the Hebrew nation and being faithful to His promises.
Things change when we move to the four Gospels of the New Testament. The word group occurs some 111 times in the New Testament and takes on a technical meaning. That meaning, which is stated by Paul, in short-hand form, in Rom 1:3-4 (see kergyma), is that the Good News of God is the Person and Work of Jesus Christ. God has come to earth as the God-man for the sole purposes of creating the mechanism for man to reconciled back to God. The Gospel is the means of salvation for mankind.
This reference to the Gospel forms the foundation for the entire letter of Romans, indeed, the entire story of Jesus coming to earth. The Gospel presupposes the discussion of Rom 1:18-3:20, for if there is no sin, there is no need for a Savior. The Gospel assures us God is really there and that He loves us and is concerned about our well-being. He has shown His love by offering us salvation through Jesus Christ.
This highlights the purpose behind Paul's writing. Paul wants us to realize that the entire message of God is about the Gospel. This point cannot be over emphasized.
The Gospel is the story of Jesus Christ and the blessings He brings to a fallen and sinful world. Many see this as the theme of Romans. And, from some points of view, this is truly the theme. When one thinks of salvation, one must turn to the Gospel to understand the implications and revelations of God.