The Matrix universe is a science fiction universe created for the movie The Matrix. The series depicts a future in which Earth is dominated by sentient machines that were created early in the 21st century and rebelled against humanity. At one point, humans attempted to block out the machines' source of solar power by covering the sky in thick, stormy clouds. During this time, the machines and mankind were engaged in a massive war in which the machines ultimately emerged the victor. Having no definite source of energy, the machines devised a way to extract humans' bioelectricity and thermal energy by growing people in pods, while their minds are kept under control by cybernetic implants connecting them to a simulated reality called the Matrix.
The virtual reality world simulated by the Matrix resembles human civilization around the turn of the 21st century (this time period was chosen because it is supposedly the pinnacle of human civilization). The majority of the stories in the Matrix franchise take place in a vast unnamed megacity. This environment is practically indistinguishable from reality (although scenes set within the Matrix are presented on-screen with a bias toward the color green), and the majority of humans connected to the Matrix are unaware of its true nature. Most of the central characters in the series are able to gain superhuman abilities within the Matrix by taking advantage of their understanding of its true nature to manipulate its virtual physical laws. More: en.wikipedia.org.