Answer: To put it simply, extremophiles are able to withstand extrmely diffiuclt environments whether its due to something like extrme high/low temperatures, or deep pressure.. These are the conditions they are able to live in. For example, you can find an extremohpile on or very close to an active volcanoe, or you can also find one in the middle of the deep sea (like certain deep sea fish).
Explanation: The environments they are able to live in are environments that humans or most animals could not possibly sustain themselves in, unless they had very special extreme adaptations for very special extreme environements.