There is 4 game modes right now, Normal (you battle random people over the world), Adventure (it's a single-player mode with lot's of bosses from World of Warcraft), Arena (you can choose 3 different classes and create a deck with random cards, then you play, each time you defeat someone you get a key, which opens a box, the more keys you have, the best the prize will be (but to play arena you will need 150 gold - or you can pay with real money), but you can only get 12 keys, and you can only lose 3 times, otherwise you are out of arena, and have to start again), and Ranked (there is 25 ranks, and above those the legend rank, you battle people around your rank, and when you win you will get a star, each rank needs a number of stars to get to a higher rank). There are 9 different classes to chose, and each classe has different cards, and different hero powers.
It's a cool game, i like it.