What is “the world” and what does the Bible say about it?

One of the meanings of the “world” is “the whole circle of earthly goods, endowments riches, advantages, pleasures, etc, which although hollow and frail and fleeting, stir desire, seduce from God and are obstacles to the cause of Christ.” (Thayer’s Greek Lexicon)

The Bible says,

"Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him. For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world." - 1 John 2:15-16 KJV

Another translation,

“Do not love this world nor the things it offers you, for when you love the world, you do not have the love of the Father in you. For the world offers only a craving for physical pleasure, a craving for everything we see, and pride in our achievements and possessions. These are not from the Father, but are from this world.” - 1 John 2:15-16 NLT

Jesus was in the world, and overcame the world.

"These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world." - John 16:33

He made a way by His death, burial, and resurrection for us also to overcome the world. We take up our cross and follow Jesus by crucifying our sinful nature by repentance, burying our old nature by water baptism in Jesus name, and rising with the infilling of His Spirit with power to overcome the temptations of this world.

"But God forbid that I should glory, save in the cross of our Lord Jesus Christ, by whom the world is crucified unto me, and I unto the world." - Galatians 6:14

We have a new life in Jesus, no longer ruled by the devil and the things of this world.

Another definition of world, pertaining to the next two verses is, "the ungodly multitude; the whole mass of men alienated from God, and therefore hostile to the cause of Christ" (Thayer’s Greek Lexicon)

"Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience:" - Ephesians 2:2

By Jesus’ name, His blood, and His Spirit, we have God’s power to overcome this world.

"Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world." - 1 John 4:4