They use the word light to describe understanding....particularly bible understanding. Psalm 119:105 speaks of the word of god being a lamp to ones feet and ones pathway and Proverbs 4: 18 speaks of the path of the righteous becoming brighter and brighter until the full light of the day.
Assuming that they are the chosen ones, whenever what they formerly claimed about the Bible doesn't come about or makes sense anymore, they change their understanding. They make it seem as though this is a good thing even though it proves that they were wrong in the past and they've shunned those who pointed it out to them years before. It's amazing that they continue to claim that whatever they currently believe, is the absolute truth and you'd better believe it and pass it along to others. Even more amazing is the fact that God once again agrees with whatever they've come up with.