We believe that through the Atonement of Christ, all mankind may be saved, by obedience to the laws and ordinances of the Gospel. (Article of Faith 3)
The laws and ordinances of the gospel are those that the resurrected Jesus teaches us: have faith, repent, be baptized, and receive and live by the direction of the Holy Ghost. And the next Article of Faith tells us that those four things are what the previous Article of Faith meant by "laws and ordinances":
We believe that the first principles and ordinances of the Gospel are: first, Faith in the Lord Jesus Christ; second, Repentance; third, Baptism by immersion for the remission of sins; fourth, Laying on of hands for the gift of the Holy Ghost. (Article of Faith 4)
However else Mormons may use the word gospel, the definition given by Jesus Christ in the Book of Mormon is foundational to them all.
Mormons differ from other Christians in significant ways, but there is little difference between us in our understanding of the gospel. We share the message that Jesus died for our sins, that we can be saved from ourselves to live as children of God rather than his enemies (Rom. 8:14; Mosiah 3:19).