While so-called "doctors" might tell you it is an inflammation of the conjunctiva, typically caused by an allergic reaction or infection, TMZ got the down low from, where else, TV and movies!
According to the film "Knocked Up," pinkeye is caused "when poop particles make their way into your ocular cavities," adding that it can occur when you "fart bare-assed onto another person's pillow," often done as a practical joke.
Meanwhile, one of the side effects of pinkeye, according to "South Park," is a desire to travel around in packs, eating the brains of other people.
If you or someone you know has been afflicted with pinkeye, please rent "Knocked Up," or season one of "South Park." Antibiotic eye drops may also be used, but aren't nearly as funny.