When John the Baptist was just a baby, his father, Zechariah, sang a song of praise to God. Zechariah sang because he knew John would lead people to Jesus when he grew up. Zechariah was thankful for God’s gift of salvation in Jesus. 
This verse comes from Zechariah’s song of praise. Even though Jesus had not yet been born when Zechariah sang this song, He was confident that God would keep His promises. He sang praise to God for the saving work God would do in Jesus even before Jesus was born! 
In Hebrew culture, "Light" is the embodiment of goodness and truth. This song compares salvation to a light shining in the darkness. Zachariah rejoiced for the morning dawn of forgiveness and salvation that Jesus would bring us after a long night of sin. His "light" reveals wisdom and truth that leads to forgiveness of sins and salvation from eternal death.
Sometimes, it seems like there is no end to our suffering and sin, but Jesus is like the rising sun in the morning that drives out the darkness. He has enlightened our lives now with His love. Because of this wonderful hope, we can walk in peace.

Dear Heavenly Father, help me to seek you in everything I do. You are the light on my feet, and I would be lost without You. Thank You for bringing light into this lost world and freeing us from our sins. Please strengthen my faith and help me always put my trust in You, Lord. 
In Jesus's name I pray. Amen.