Enlightenment is the process of decreasing one's knowledge about a particular subject. It entails becoming more stupid about something, attaining the state of emptiness, or "no-mind."
This state is considered very pleasurable, hence the common saying "ignorance is bliss."
A common cause of enlightenment is spending many hours playing Computer Games or being on this site, among other things.
How to become enlightened
There are many ways to become a enlightened, although for some it is a long and tedious process. Some people believe that enlightenment comes through many hours of prayer and meditation, although modern enlightenment science suggests that to become enlightened, one (as in a person, or other entity, excluding organizations, animals, plants, and everything except people) needs to preform a form of research, on a reliable source of information, such as the Internet, or even by preforming research using less reliable sources of content such as Wikipedia.
Some rather intelligent people out there  declare, sometimes quite vocally that enlightened can be gained through other means, such as Computer Games and Google. The beings who believe these theories preferred to be known as the Computer Games cause Enlightenment (sect), although they usually don't mention that they're a sect, and if they do, they usually don't do so in brackets.
Since enlightenment exists in the eternal 'now', the entire history of mankind has been an illusion. There has never been a past, nor will there be a future. It is only the mind, with it's constant meandering that creates the illusion of the passage of time. The current location of 'now' is June 6th, 1978. We have been living in an illusion ever since. The first person to reach enlightenment was Drinkus Alcoholicus, the great Roman Hobo Prophet. He managed to drink himself into a coma and then beat the God of Death and Trickery, Bill Maher, in a game of beer pong. This allowed Drinkus to reach a state of Nirvana.