Summary: Jesus is the true light of the world.
There was a man sent from God, whose name was John. This man came for a witness, to bear witness of the Light, that all through him might believe. He was not that Light, but was sent to bear witness of that Light. That was the true Light which gives light to every man coming into the world.
John was sent by God to bear witness of His Son Jesus. His Son was the True Light and He was in the world but unfortunately the world did not recognise Jesus as the True Light.
Jesus as the true light was sent to the world by His father and He came to bring us back to the Father but because there was so much darkness in the world so many refused to acknowledge Him as the true light of the world.
We are to believe that God is real through His Son Jesus Christ. God sent His Son as the true light and took us out of darkness according to Colossians 1:13
He has delivered us from the power of darkness and conveyed us into the kingdom of the Son of His love. - NKJV
He rescued us from the power of darkness and brought us safe into the kingdom of his dear Son - GNT
Therefore, according to this chapter we have been rescued from the kingdom of darkness into the kingdom of His Son whom He loves. In the kingdom of His Son there is no darkness at all only light.
But I saw no temple in it, for the Lord God Almighty and the Lamb are its temple. The city had no need of the sun or of the moon to shine in it, for the glory of God illuminated it. The Lamb is its light. And the nations of those who are saved shall walk in its light, and the kings of the earth bring their glory and honor into it. Its gates shall not be shut at all by day (there shall be no night there).
The Amplified version puts it this way:
I saw no temple in it, for the Lord God Almighty [the Omnipotent, the Ruler of all] and the Lamb are its temple. And the city has no need of the sun nor of the moon to give light to it, for the glory (splendor, radiance) of God has illumined it, and the Lamb is its lamp and light. The nations [the redeemed people from the earth] will walk by its light, and the kings of the earth will bring into it their glory. By day (for there will be no night there) its gates will never be closed [in fear of evil].
Jesus is the true light.
A time would come that there will be a new city ( Jerusalem ) and in this place the Lord God Almighty and the Lamb are it's temple. In this wonderful city we would not need the sun or the moon to shine in it. The glory of God and the Lamb - who is Jesus will be the light and there won't be no night there.
can you imagine a place that there would be no night and just the glory of God and the Lamb is it's light?
That is why Jesus came to save us from the kingdom of darkness into His kingdom.
What a glorious time that will be! To be in His presence forever and not see any form of darkness again but Jesus who is the light of the world.
This is why we are to hate anything to do with darkness and Jesus said so in John 3:19.
And this is the condemnation, that the light has come into the world, and men loved darkness rather than light, because their deeds were evil. - NKJV
And the judgement is based on this fact: God’s light came into the world, but people loved the darkness more than the light, for their actions were evil. - NLT
The light has come into the world, and people who do evil things are judged guilty because they love the dark more than the light. - CEV
There will be a day of judgement according to John 3:19 where those who love darkness rather than light will be judged. But Jesus came to show us the right path to walk as the light of the world.
He said in John 8:12
Then Jesus spoke to them again, saying, “I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life.” - NKJV
Jesus spoke to the people once more and said, “I am the light of the world. If you follow me, you won’t have to walk in darkness, because you will have the light that leads to life.” - NLT