"Digimon" are "Digital Monsters". According to the stories, they are inhabitants of the "DigiWorld", a manifestation of Earth's communication network. The stories tell of a group of mostly pre-teens, who accompany special Digimon born to defend their world (and ours) from various evil forces. To help them surmount the most difficult obstacles found within both realms, the Digimon have the ability to evolve (Digivolve) In this process, the Digimon change appearance and become much stronger, often changing in personality as well. The group of children who come in contact with the Digital World changes from series to series.