Like all of the Mortal Kombat games, MKII is about warriors fighting in a tournament for inspecific power and fame. Shang Tsung is chosen for his ability to transform into other characters.
This movie aims to demonstrate as many quirks and fatalities of the game as possible. Examples include two Shang Tsungs with a Raiden child, a headless Reptile eating Kitana's head and a bloody clone of Jax. The AI is also humiliated.
The author's comments page is a definitely recommended reading for this movie.
Note: The movie contains semi-realistic violence to be expected with the Mortal Kombat series.