The Walking Dead is a cinematic interactive story set in Georgia during a zombie apocalypse. The game incorporates elements of first-person shooters and point-and-click-adventure games, but focuses primarily on the plot consequences of the player's action and dialogue choices in-game, in the style of a role-playing game.
Segments of gameplay are released episodically; as of this review, the game consists of the five episodes of Season One, with a bonus episode and Season Two due for release in the near future. Even when purchased as a season, the game retains its TV-like episodic structure, complete with previous episode summaries at the beginning and next episode summaries at the end of each. (Slightly ironic given that it's based primarily on the comic - as opposed to The Walking Dead: Survival Instinct, a distinctly different game based on the TV series, which in turn was based on the comic. Oh franchising, how funnily you function.)
Gameplay itself consists mostly of dialogue choices for the protagonist, although you may be called upon to explore an environment, aim a blow, solve a situated puzzle, or make a grab for an item in the scene within time constraints. Dialogue choices are also usually governed by time constraints, although silence is always an option (if not always the best) in such cases.
Sam's Related Factoid: The classic film Night of the Living Dead is perhaps most responsible for the modern popularized conception of zombies. It was also notable for starring an African-American hero protagonist, something that remains rare in theaters to this day. Props to Telltale for bringing brown skin to their similarly watershed video game and for not being afraid to reference it within the game's dialogue.