In the basic game play (the only one currently available), you have 30 levels of increasing difficulty (level 1 being roughly on the outer limits of an average high-school student vocabulary, and level 30 being insanely difficult unless you are either an absolute genius or the exact opposite of it). Each level consists of 12 rounds.
In each round, you get 12 sets of four words, and you have 60 seconds to pick those 12 words you believe are real. For each round, you can pick the category, and all words in one round come from the same category.