Portal 2 was an instant hit after the first game-Portal. Portal is a puzzle-platform single player game to try to escape Aperture Laboratories, and the games that they have prepared for the character that you control through the game, Chell. later in the game, you are told to use a cube, that most people call the "Companion Cube". Portal 2 is a co-op game along the same story line of escape and play games. The characters that you play with are: a female robot named P-Body, and a male robot named Atlas. In both of these games, GLaDOS, a robot (that obviously has something against you) that will guide you across your missions. There are many different takes on the game, and many YouTubers do Let's Plays on them, or game theories.
Go ahead and check out one awesome YouTuber that I watch daily- The Game Theorists- It really makes you think about the games that you play.