This document discusses unidentified flying objects (UFOs) and the possibility of alien life. It defines a UFO as any unidentified object seen in the sky and outlines some common shapes reported. The document also defines aliens as any extraterrestrial life not originating from Earth. It briefly summarizes some historical UFO sighting events and proposes the ancient alien theory that aliens may have visited Earth long ago and influenced human civilization, pointing to some archaeological evidence. The document considers the possibility that aliens may be disguising themselves as humans or that their presence could cause changes to conditions on Earth or conflicts.