From the introduction:
Digimon is a series which is primarily defined by what's usually the most obvious about it: a monster taming and battling type of series, where humans and monsters partner up to defeat the forces of evil. But there's a bit more to it than meets the eye, it's also a series about personal growth, and discovering a bit more about yourself, as well as some strong themes about teamwork, friendship, and cooperation. It tends to set itself apart from other Monster Tamer types of franchises primarily by each Human generally being partnered with just one to three Digimon (at least at a time) over collecting hundreds of thousands of monsters. It tends to give a more personal feel to the Digimon and their partner, as well as giving a bit more time to develop the character's personalities and backstories.
User summary:
This "Version 0.09" edition is an expanded and revised version of the game incorporating many refinements suggested by a broad audience. Widely circulated and generally available, it is perhaps the best-known edition of the rules.