Colossians 1:18

And he is the head of the body, the church. He is the beginning, the firstborn from the dead, that in everything he might be preeminent.

-Colossians 1:18

He is also the head [the life-source and leader] of the body, the church; and He is the beginning, the firstborn from the dead, so that He Himself will occupy the first place [He will stand supreme and be preeminent] in everything.

-Colossians 1:18 (AMP)

I guess this one isn't too complicated.  Jesus "is the head of the body, the church".  The body is the same thing as the church, so it is saying that Jesus is the head of the church.  In what way is he the head, or what does it mean to be the head?  I like how the Amplified version gives its opinion: "the life-source and leader".  I guess it's also no coincidence that the idea of a head with respect to a body is placed here.  Maybe the simplest way I'd put it is to say that what Jesus is to the church is what a head is to a body.  Does a body live without a head?  What does the head do for the body?  The head has eyes, ears, mouth and nose.  So, most senses are taken from the head.  More importantly, a head has a brain.  We are the church, are we not?  Jesus is our head and it is important that we value and treat him as such.