The word “gospel” means “good news that is announced.” That makes it different from other religious messages, which might be called “good advice to be followed.”
The good news is that we are so lost and broken that we cannot find God or fix ourselves, so God has come to find and save us. To do that he became a man, Jesus of Nazareth, who lived an ordinary human life, distinguished only by the startling fact that he never did anything wrong. He kept all of God’s laws, both internally and externally, and having done so, he transferred all the credit for that obedience to those who love and trust him.
In addition to giving us the credit for his perfect life and obedience, Jesus went further and willingly took the punishment that was due to us for our imperfect, rebellious lives. Dying on the cross, he forgave those who were killing him. When he rose from the dead, Jesus demonstrated that death had no hold on him, nor on any who entrust their lives and souls to him.