A: “Protoevangelium” comes from two Greek words: “protos” meaning “first” (i.e. our word “prototype”), and “euaggelion” meaning “Gospel.” In other words, it is the first mention of the Gospel in the Bible. This first mention is found in (Gen 3:15), which says: “And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.”
Although interpretations of this verse vary a little, most agree that the “enmity” is between “thy seed” (Satan and his followers) and “her seed” (Jesus Christ, who was a descendant of Eve).
Satan “bruised his (Jesus’) heel” by attacking Him in numerous ways during His time on Earth, which ultimately ended with Him suffering and dying on the cross. However, through His resurrection, Jesus won the decisive victory, and “bruised the head” of Satan. “Bruising the head” was a fatal blow, meaning that Satan was defeated once and for all. His time on Earth will soon end, and He will be cast into the Lake of Fire (Rev 20:10).
Thus, we see that from the very beginning, God had a plan to redeem mankind from the penalty of sin through Jesus Christ. This theme runs throughout the whole Bible. Jesus Christ was “manifested” to “destroy the works of the devil” (1 Jn 3:8) (Also see: Heb 2:14-15, Col 2:15)