Other mistake: In the English dub of the series, Tai's last name is Kamiya; however, when he makes reference to the family name plate his father put on the front door in this episode, the name displayed is Yagami. (00:03:00)
Other mistake: The DigiDestined refer to Arukenimon by name before she formally introduces herself. Before her introduction, it is not established that the strange woman is in fact a Digimon.
Answer: Digimon started as a series of virtual pets, making them digital. In the television series, Digimon live in the "digital world."
Bishop73