What Is The Gospel and what does it do?

I am not ashamed of the gospel, because it is the power of God for the salvation of everyone who believes : first for the Jew, then for the Gentile; for in the gospel a righteousness from God is revealed, a righteousness that is by faith from first to last, just as it is written: "The righteous will live by faith; " for in Christ all the fullness of the Deity lives in bodily form, and you have been given fullness in Christ, who is the head over every power and authority; in him you were also circumcised, in the putting off of the sinful nature, not with a circumcision done by the hands of men but with the circumcision done by Christ, having been buried with him in baptism and raised with him through your faith in the power of God , who raised him from the dead; for we know that our old self was crucified with him so that the body of sin might be done away with, that we should no longer be slaves to sin because anyone who has died has been freed from sin. (Only one period, means only one sentence.)