Flat design and skeuomorphism

This is something new. I have never heard about this before. Apparently, in the design world, there are two ways to design. Flat design and Skeuomorphism. What is the difference ?

According to Web Designer Depot :

In plain terms, flat design is a style of interface that doesn’t employ any three dimensional realism. Windows 8 is the perfect example, being, as it is, entirely flat.

Flat design advocates consider the leather strip across the top of your iPhone’s screen in the Notepad app, or the debossed lines in the Reminders app, as examples of skeuomorphism; they are examples of translating features from one discipline to another. Flat design employs no gradients, bevels or shadows to simulate three dimensional design (as screens are two dimensional).

I am not sure it really matters a lot. It really depends on the website concept. Flat design is good, in terms of simplicity. Skeuomorphism is good when it comes to showing off. So, both have their own advantages.

What do you think ?