Complex sentence: It is the second game in the "Borderlands" series and the sequel to 2009's "Borderlands" and was released for the Microsoft Windows, PlayStation 3, Xbox 360 and OS X platforms.
Split into simpler sentences: It is the second game in the "Borderlands" series and the sequel to 2009's "Borderlands". The game was released for the Microsoft Windows, PlayStation 3, Xbox 360 and OS X platforms.