The book of Colossians is another of Paul's letters to the many churches of his day, and this one focuses a lot of its attention on Christ and on how he must be central to a believer's life.
Chapter 1 dives right into some serious doctrine related to God's son: "Who is the image of the invisible God, the firstborn of every creature: For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him: And he is before all things, and by him all things consist" (1:15-17). This passage kind of goes over my head the first time I read it. I'm not used to thinking of Jesus in this way, as someone powerful and preeminent, though scripture clearly shows that he is these things...it's just easier for me to think of the Lord in his humble and sacrificial mode.
The next couple of verses show that Jesus' power, both in heaven and in earth, has been approved and set up by God the Father: "For it pleased the Father that in him should all fulness dwell; And, having made peace through the blood of his cross, by him to reconcile all things unto himself; by him, I say, whether they be things in earth, or things in heaven" (1:19-20). It is because Jesus has this God-given power and authority that he is able to provide forgiveness of sins.
Paul talks to the Colossians one-on-one a little more in chapter 2. It seems that, unlike several other churches, Paul has never physically visited the Colossians or their neighbors the Laodiceans, so he's all the more invested in communicating with them and providing them with some helpful doctrine. In chapters 3 and 4, Paul's counsel is mainly of a practical nature, telling the Colossians the sort of attitudes and actions they should avoid, then telling them the sort of behaviors they should embrace: "And above all these things put on charity, which is the bond of perfectness. And let the peace of God rule in your hearts, to the which also ye are called in one body; and be ye thankful." (3:14-15). Charity means "love", so Paul is saying that loving others is the very essence of a righteous attitude. I also like the phrase "let the peace of God rule in your hearts", because it's so easy to let your heart be taken over by worries instead of letting the peace that the Lord provides sink in.