Matthew 1:1, Mark 1:1; and John 1:17 all use the words "Jesus Christ" together in their Gospels. Luke, never uses "Jesus Christ," but his Gospel clearly presents Him as such (Lk. 1:32; 2:11). The Gospels are statements of eyewitnesses, testifying to the death, burial, and resurrection of the Son of God, all according to what the Scriptures had prophesied (1 Cor. 15:1-11).
Why is the Gospel called the "Good News?"
It is called that because God's Word says all of us are sinners, and as such, we must be sentenced to die; but because Jesus died in our place, we don't have to die for our sins (Rom. 3:23; 5:8; 6:23; 8:1; 2 Cor. 5:21). It is "Good News," because we are taught by the Scriptures of our inability to perfectly obey God's Law, and therefore, without the sacrifice of Christ, we would be doomed to an eternity in the Lake of Fire (Gal. 3:24; 1 Cor. 15:17; Rev. 20:11-14). God has done the necessary "work" to purchase our salvation, not only because we, ourselves, are incapable of doing so, but because if we were able, we would take credit for the righteousness that is a gift from God (Eph. 2:8-9).
When and how does the Gospel work?
Jesus taught that the Holy Spirit, on occasion, convicting us of sin, righteousness, and judgment, moves us to place our trust in Him, Jesus, and when we do, we become a new creature; we are spiritually born again (Jn. 3:3-8; 16:7-15; 2 Cor. 517). When the Gospel, "the power of God unto salvation," is preached, those who believe what they hear are said to have faith; faith in Christ produces salvation (Rom. 1:16; 10:8-17). "Salvation" is the word we use to describe the moment one is saved from the penalty due them for their sins. In Christ, we are saved from the penalty of our sins; we are being saved from the power of sin over us, and we shall be save from the presence of sin forever (Rom. 6:23; Gal. 5:16-25; 1 Jn. 3:2; Rev. 19:8).
However, it is possible to believe that Jesus is the Son of God, that He died, was buried, and was raised from the dead, without being saved. The Bible says Satan believes, and yet he has chosen to reject Jesus as authority over him (Jam. 2:19-26). Notice that salvation comes from a faith that is displayed by a changed life. Believers are to stop sinning and do good works (2 Tim. 2:19; Eph. 2:10)!
We are not saved by works, but saved people do good works!