"You are the light of the world. A city that is set on a hill cannot be hidden.
Nor do they light a lamp and put it under a basket, but on a lampstand, and it gives light to all who are in the house.
Let your light shine before men, that they may see your good works and glorify your Father in heaven."
Matthew 5:14-16 (NKJV)
Lighthouses were used more in the past that they are today, but lighthouses can still be found in some places. Originally, lighthouses were used to help guide ships, and today much of that same guidance comes through technology. A lighthouse had a light that would shine so that sailors could see the way that they needed to go. Without this beacon of light from the lighthouse to help people navigate their ships, it would have been harder for the sailors to know which way to go to safely reach their destination.
Jesus said that we are the light of the world, we are a beacon of light for others. Based on what Jesus said in Matthew 5, we are those who must provide the light that the world needs. In the same way that ships would not have a light to guide them if the lighthouse was taken away, the world will not have the light it needs if we do not shine our light. So many people in the world are floating aimlessly through life with no real direction. They need the light we can, and should, bring to help them to see where to go.
In John 9:5, Jesus said He was the light of the world, and we need to reflect the light of Jesus to others. In Psalm 119:130 it tells us that the entrance of God's Word brings light, and we need to bring the light of the Word to the world. If we as believers do not shine our light, then there will not be any light for the world. One of our great responsibilities in life as Christians is to bring the light of Jesus the Savior to the world and the light of God's Word to the world, it is up to us to be a beacon of light.