Extraterrestrial life is -- simply put -- life that is not from Earth and generally refers to life that is not native to the planet in question. The more commonly used term for such life is alien. As of yet, we have not discovered extraterrestrial life, although it could possibly exist in several worlds in the Solar system, and -- with trillions upon trillions of stars out there and the elements that are the fundamental parts of life out there being in such abundance -- it is quite likely that the processes of life started somewhere out in space.
Extraterrestrial Life in Science Fiction
Like robots and space travel, extraterrestrial life is one of the most common concepts in science fiction. However, often due to a lack of creativity or budget constraints on special effects departments, alien lifeforms in science fiction are often highly anthropomorphic. A few examples, including Chiss and most races in Star Trek, are even capable of cross-breeding. Leaving aside the breeding, this is still incredibly unlikely, given that we would have more in common with daylilies genetically. Life could have taken thousands of other viable paths, such as creatures being radially symmetric instead of bilaterally symmetric .