Colossians 1:19

"For God was pleased to have all his fullness dwell in him," NIV translation

Jesus was both fully God and fully man even though this may be hard for us to understand. He was fully God in that He has all of the same characteristics of God (the DNA) yet He came to this earth as a man.

This fact is how we can tell those that truly are God's children from the imposters that have gone out to deceive many. (see 1 John 4).

Colossians 1:20

"and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross." NIV translation

The penalty for sin always has been death and all things were tainted by sin. To have a right relationship with God (be reconciled) required the payment for sin. The Old Testament sacrifices were for individual sins and were only temporary while victory over all sin was accomplished once and for all time by Jesus on the cross.

Colossians 1:21

"Once you were alienated from God and were enemies in your minds because of your evil behavior." NIV translation

Before we come to faith in Jesus Christ, our minds are focused on ourselves and on things of the flesh. This makes us enemies of God because it leads to all kinds of evil actions. This verse reminds us of just how bad sin is. Oh, it may seem like fun for a season but, even then, it is separating us from God and causing us to be His enemies. When we come to Christ, we have a renewal of the mind. This word renewal is like when you remodel a house. You take the old stuff out and replace it with new stuff and that is what happens through the Holy Spirit.