D&D Next, is a playtest of the soon to be published (Fall 2014) Dungeons and Dragons 5th edition by Wizards of the Coast. D&D Next is a heroic fantasy RPG inspired by the mechanics and setting of all previous D&D editions.
The final playtest packet was released in September 2013 and is no longer available. Every iteration of the playtest tweaked the core rules and the classes to try out different mechanics. The final version of the product will ship with multiple rules modules to customize the play of the game to meet your group/table's preferred style.