What is skeuomorphism?

 "an element of design or structure that serves little or no purpose in the artifact fashioned from the new material but was essential to the object made from the original material"
Basalla, George (1988). The Evolution of Technology. Cambridge, UK: Cambridge University Press. p. 107ISBN 0-521-29681-1.

Skeuomorphism - very difficult word to spell and say - is a key concept in contemporary design. Until this week it was seen as one of the core concepts behind the success of Apple. 

The skeuomorphic principle is that innovation works best when it is presented in a familiar form. An ebook, for example, mimics the physical appearance of a book, even though this is not technically necessary.

Steve Jobs skeuomorphic approach to design was a key element in transforming  previously geeky gadgets into must-have accessories - MP3s into iPods for example. Later Sir Jonathan Ive took 'a hatchet to the skeuomorphic design principles of iOS' - see here 
Many designers welcomed this change.  Yves BĂ©har, for example, objected to Apple's former wooden digital bookshelves: 
 "The digital bookshelf doesn’t really work like a bookshelf," he said. "You’re throwing all this extraneous visual noise at me and it’s confusing. My brain, which is used to the physical bookshelf, is confused because of the differences in usability. It’s cute, but not particularly useful." source