DUDE uses regular playing cards for task resolution instead of the dice common in other games, and by holding different-sized hands, each player has more or less control over the results of their actions, rather than being at the mercy of blind chance.
DUDE can theoretically represent any genre. However, it does work best at fast action-adventure stories or freeform dramatic gaming; complex mechanical simulation of a world is not within DUDE's abilities.
DUDE uses a unified task system to handle all actions. And unlike other (overly-complex) games, it doesn't waste your time trying to remember which stat affects a task.
DUDE is only the basic mechanics of an RPG - you will need to acquire or write a setting book. See The Alan Smithee Project for an example of what needs to be developed in such a book.