The word gospel simply means good news. It's the good news of God about the Lord Jesus Christ (1 Corinthians 15:1-4). It's good news because Christ died on the cross to save believers from the judgment of sin. It's good news because God gives believers eternal life, through the Lord Jesus Christ. Jesus is risen from the dead to give believers everlasting life.
Christ is for all nations. The salvation of Jesus Christ is sufficient for all. Yes, all are sincerely invited to Christ. Most assuredly, the gift of eternal life in Christ is certain for all who repent and believe. Therefore, the good news must be preached to all nations and people without exception (Matthew 28:18-20).
Christ is freely offered to all, but all are not saved. "And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil" (John 3:19). All people will simply not come to Christ, but many are certain to come to Him. None who come to Him will be turned away (John 6:37).
Yes, the Gospel of Christ is preached to all nations. That certainly doesn't mean that everyone is saved without believing on the Lord Jesus Christ (Acts 16:31). It does mean that the death of Jesus Christ for our sins effectively saves all who believe. Christ risen from the dead saves all who call upon him (Romans 10:9-13). Therefore, the Gospel of Christ must be preached to all nations and people everywhere (Mark 16:15).
