The Gospel (Good News) Simple terms; Believe on Christ and live. The Gospel (Good News) Basic Scriptural terms; Romans 3:23, Romans 6:23, I Corinthians 15:3-4, John 3:16, 36. Ephesians 2:8-9, Ephesians 1:13, I John 5:11-13.
The Gospel (Good News) in Layman terms; All have sinned (fallen short of God's mark) which is perfection. Yet in-spite of such, God loves us so much, that He was manifest in the flesh (Jesus the Christ), being the lamb of God, which takes away the sin of the world. This He did at Calvary, being our atonement, and our propitiation, paying in His own blood to redeem us, and cleanse us eternally. He then, did go into the heart of the earth for three days and three nights, and upon the third day, did rise in resurrection power. And all who believe on/in Him, and what He has done and promised, will pass from death unto life, and will also be sealed with Him, the Holy Ghost. Not only that, all who have believed on/in Him, have the eternal promise and assurance, that we may know, that we have been saved forever. I bid;
I John 5:11-13: And this is the record, that God hath given to us eternal life, and this life is in his Son. He that hath the Son hath life; and he that hath not the Son of God hath not life. These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God. May Christ alone be exalted.