Extraterrestrial life is life that is not native to the Earth. In other words they are "aliens". But for life to evolve, it needs water. If it was life in the universe, it would range from bacteria like organisms to intellegent beings far more advanced than humans. Life can be found in either icy worlds with subsurface oceans, in the ice caps of Mars or a Mars like planet, or planet/ moon with continents and oceans. But they are different forms of life. It could be extremophiles which can be found in Venus, or Titan. But the most important forms are the life forms that are Earth-like. They can be found in extraterrestrial liquid water. Are we alone in the universe? That is what people have been asking for centuries. But according to what planets and moons we see in space, there could be a chance of the answer being "no". In other worlds, you might not see the same plants and animals as you see on Earth. Life on even on the most earth like worlds could evolve differently