In Rolad Dahl's book Charlie and the Chocolate Factory and its two film adaptations (Willy Wonka and the Chocolate Factory and the one with Johnny Depp) the Wonka Bars are the flagship products of Willy Wonka's candy empire.
In the book, Charlie's Grandpa Joe mentions that there are over 200 varieties of Wonka Bars.
They play an important part in the plot of story, because the Wonka Company has hidden five golden tickets in the packaging of random bars and whoever finds them gets to go on a tour of the factory, which has been closed to the public for years. This announcement leads almost everyone around the world into a scramble to find them.
The popularity of the book and movies has lead Nestle to make a real Wonka Bar, under its Willy Wonka Candy Company brand. The Wonka bar they make is milk chocolate with pieces of graham cracker inside.