1. Good News:
The most common meaning is simply "good news." This is the original meaning of the word "gospel" in Old English and is still how it's often used today. For example, you might say "The gospel of a new cure for cancer is spreading fast."
2. The Christian Gospel:
In Christianity, "gospel" refers to the message of salvation through Jesus Christ. It specifically refers to the accounts of Jesus' life, teachings, death, and resurrection as recorded in the four Gospels of the New Testament: Matthew, Mark, Luke, and John.
In summary: The word "gospel" generally means "good news," but in Christianity, it has a specific meaning referring to the message of salvation found in the New Testament Gospels.