The 'Gospel'
(A word from the Latin, 'evangelium',
meaning, "a good or joyful message".)
is,
The story of the life of Jesus Christ; including the revelation of God's grace to fallen man and
His plan of salvation through
His Son (Jesus Christ),
as revealed by
Jesus and His
apostles.
...For I am not ashamed
of the gospel of Christ:
for it is the power of  God unto salvation
to every one that believeth;
to the Jew first, and also to the Greek.

Romans 1:16