The aliens superficially resemble walking, rotting corpses. John Carpenter didn't want the aliens to look like the high-tech creatures of other science fiction films. He decided that since these beings were corrupting humanity, they themselves should resemble corruptions of human beings.
Cinema, short for cinematography, is often used to refer to the industry of films and filmmaking or to the art of filmmaking itself. The contemporary definition of cinema is the art of simulating experiences to communicate ideas, stories, perceptions, feelings, beauty or atmosphere.