The gospel when translated from the Greek means "the news about a kingdom or the exploits of a king". The gospel to believers is the news about the kingdom of God, or what God has done in Christ.

Mark 16:15-18
[15]And he said unto them, Go ye into all the world, and preach the gospel to every creature.
[16]He that believeth and is baptized shall be saved; but he that believeth not shall be damned.
[17]And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;
[18]They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover.

The gospel itself is supernatural. It's is the demonstration of the spirit and the power of God.

1 Corinthians 2:4-5
[4]And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power:
[5]That your faith should not stand in the wisdom of men, but in the power of God.

So what exactly is the gospel?
1 Corinthians 15:3-4
[3]For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
[4]And that he was buried, and that he rose again the third day according to the scriptures:

The true gospel is the message of the death, burial, and resurrection of Jesus. No extra thing added. No motivational speaking or scary stories intended to persuade. It is the message of God's love.

When the gospel is preached, the holy spirit convinces people of the truth of the gospel. Whoever now believes becomes born again instantly. The spirit of God begins to dwell in him forever.

Ephesians 1:13
[13]In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise

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Harshirama:
The gospel when translated from the Greek means "the news about a kingdom of the exploits of a king". The gospel to believers is the news about the kingdom of God, or what God has done in Christ.
....
The gospel itself is supernatural. It's is the demonstration of the spirit and the power of God.
.....
So what exactly is the gospel?
....
The true gospel is the message of the death, burial, and resurrection of Jesus. No extra thing added. No motivational speaking or scary stories intended to persuade. It is the message of God's love.

When the gospel is preached, the holy spirit convinces people of the truth of the gospel. Whoever now believes becomes born again instantly. The spirit of God begins to dwell in him forever.

Wrong! The Gospels is instead God's New Covenant Law, an agreement between God and individuals(not groups) for living in the Kingdom of God.