The Digimon Card Game isn't half is popular/expensive as the Pokémon Card Game! Even thought the basic idea is the same, people don't find these cards as valuable, by this I mean no one has been murdered over them or no one sells them for big bucks!
The basic idea is to collect the right items, such as Digivices, to digivolve your favourite digimon into a bigger, stronger, cooler fighting monster!
If the player knocks out all of the other player's Digimon, they are claimed Champion of that round!
All in all a very fun/addictive game ^_-