The Orange Box includes all the content of The Black Box, plus the original Half-Life 2 and Half-Life 2: Episode One.
Half-Life 2: Episode Two -- the second installment in Valve's episodic trilogy advances the award-winning story, leading the player to new locations outside of City 17.
Portal -- a pioneering type of single player action game that rewrites the rules for how players approach and manipulate their environment - much like how Half-Life 2's Gravity Gun reinvented the way gamers interact with objects in the game.