A person comes to the conclusion that life means to feel the light, and death is the perception of the darkness, or the Creator’s absence from his perceptions. Before a person comes to the genuine understanding of what is good and what is bad, he first goes through many different states.
The Machsom is the barrier that blocks the light from entering our world. How is the Machsom different from the Masach (the screen)? The Masach is characterized by an attribute that is totally different than the Machsom. In front of the Machsom, there is the light in its entirety, and nothing conceals it. There, the person himself pushes the light away with the force of his desire to not receive the light for the sake of self-gratification.
Courtesy of http://www.youtube.com/watch?v=6hLLZfnulSU