(This is a general interpretation of Holy Scripture. Please do not take our word as law as there is only one Law and that's the Word of G-D and Christ. Please read the scripture for yourself, pray, atone and enter into the Kingdom of Heaven.)
This is the quintessential moment in the Gospel that Jesus' divine nature revealed itself, something that could be seen by other men. Jesus brought light to this dark world and as I believe Jesus was the first light created by G-D in Genesis 1-3, buts that my personal belief. But we all will shine bright as stars in front of G-D when we pass.
The people that Jesus speaks with may be clue as to whom the two witnesses may be in the prophecy of Revelation 11.
1. And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
2. And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light.
3. And, behold, there appeared unto them Moses and Elias talking with him.
4. Then answered Peter, and said unto Jesus, Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles; one for thee, and one for Moses, and one for Elias.
5. While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.
6. And when the disciples heard it, they fell on their face, and were sore afraid.
7. And Jesus came and touched them, and said, Arise, and be not afraid.
8. And when they had lifted up their eyes, they saw no man, save Jesus only.
9. And as they came down from the mountain, Jesus charged them, saying, Tell the vision to no man, until the Son of man be risen again from the dead.
We can all shine bright as the sun as we move closer and closer to G-D through his wisdom. We must be continuously improving our lives so our light grows bigger in this dark world. The goal is to transform into light when that day comes and to rest among righteous.