Jesus Christ is our light! Jesus is the source of all that is good and he calls us to communion with him, his Father, and the Holy Spirit.
Jesus Christ is the source of purpose for the Church and everything the Church does and says is in relation to him. We call this Christocentricity.
We are called, as Christians, to continue the most holy life which Jesus led on earth: we must look to Jesus, love like he loved, and live as he lived.
Jesus Christ is the light of the nations and the Church reflects and shares that light with all.
The introduction to the Dogmatic Constitution on the Church, Lumen Gentium, explains:
Christ is the Light of nations. Because this is so, this Sacred Synod gathered together in the Holy Spirit eagerly desires, by proclaiming the Gospel to every creature, to bring the light of Christ to all men, a light brightly visible on the countenance of the Church. Since the Church is in Christ like a sacrament or as a sign and instrument both of a very closely knit union with God and of the unity of the whole human race, it desires now to unfold more fully to the faithful of the Church and to the whole world its own inner nature and universal mission. This it intends to do following faithfully the teaching of previous councils. The present-day conditions of the world add greater urgency to this work of the Church so that all men, joined more closely today by various social, technical and cultural ties, might also attain fuller unity in Christ.
Watch this episode on the Second Vatican Council introducing the significance of Lumen Gentium and its' Christocentric proclamation: "Jesus Christ is the light of nations..."