The
'Light of the World'

is,

The Body of Christ;
All Christian believers who are filled with God's Light, Truth, Love, and Spirit.

Ye are the salt of the earth: but if the salt have
lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men. Ye are the light of the world. A city that is set on an hill cannot be hid. 
Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light
unto all that are in the house. Let your light
so shine before men, that they may see
your good works, and glorify
your Father which is
in heaven.  
Matthew  
5:13-17