According to Wikipedia:
Wayang Kulit is a very unique form of theatre employing the principle of light and shadow. The puppets are crafted from buffalo hide and mounted on bamboo sticks. When held up behind a piece of white cloth, with an electric bulb or an oil lamp as the light source, shadows are cast on the screen.
Wayang Kulit plays are invariably based on romantic tales, especially adaptations of the classic Indian epics, “The Mahabarata” and “The Ramayana”. Some of the plays are also based on local happenings (current issues) or other local secular stories. It is up to the conductor or “Tok Dalang” to decide his direction.
The Dalang is the genius behind the entire performance. It is he who sits behind the screen and narrates the story. With a traditional orchestra in the background to provide a resonant melody and its conventional rhythm, the Dalang modulates his voice to create suspense thus heightening the drama. Invariably, the play climaxes with the triumph of good over evil.
The modern wayang kulit is actually quite elaborate, but it still sticks to its historical roots. It is still a form of theatre and a platform for story-telling. The electric bulb or oil lamp has been replaced with the technology of rear-projection screens like that used in the Smart Board 3000i. Instead of having a shadow play, we now have Powerpoint slides and Flash animation. Instead of having puppets made of skin, we now have life-sized skin puppets on a string.
However, the Dalang is still the genius behind the entire performance and his job is to sell
vapourware hopes and dreams.