The English word "Gospel" has origins in a word meaning "good news." When you hear Christians talk about the "good news," or Gospel, of Jesus Christ, they are referring to the works that God accomplished in sending His Son to the world to provide a path for redemption of sin. Christians believe that all humans are sinful, and therefore stand in judgement of that sin by their Creator. However, they believe God sent His Son to Earth to live as a man and ultimately sacrifice His life as a means of restoring the relationship between humanity and God. The "good news" is that anyone who believes that Christ came to Earth as the Son of God and who confesses his or her sin to God can live eternally with God.
Salvation in the Christian view is the acceptance of Christ and the turning away from sin. The choice to follow Christ is the point of salvation. This doesn't mean that Christians live sinless lives (as that is impossible), but does mean that a person who has chosen salvation should have a life that bears the fruits of the spirit. Those qualities are found in Galatians 5:22-23: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control. The gift of salvation is only accomplished through faith in Christ.
The Gospel, then, encompasses the life, teachings, and sacrifice of Christ. Salvation is a personal decision to believe in and follow Christ.