Extraterrestrials, often referred to as aliens, are hypothetical beings that originate from outside Earth. They are a popular subject in science fiction and are often depicted as having advanced technology and intelligence. Scientists search for signs of extraterrestrial life through various means, including the study of Mars and the exploration of distant planets and moons. The search for extraterrestrials includes projects like SETI (Search for Extraterrestrial Intelligence), which listens for signals from other civilizations. While no definitive evidence of extraterrestrial life has been found, the vastness of the universe suggests that it is possible for life to exist elsewhere.