The glory of Christ is what He willed and accomplished for us by enduring the cross and raising Himself from the dead - sonship in the New Birth by His Holy Spirit as joint heirs of all that the Father has.     

What world is John talking about?     
He is talking about the people on earth who are Carnal Minded having never received the Gospel of Jesus Christ.     

Those who are Carnal Minded cannot understand those who have become Spiritual Minded by receiving the Truth and being Born Again.