Websites designed in the flat style, one of the popular trend of the last years within web design.
Apple made the so-called skeuomorphism style popular with a new version of their iOS. Elements were designed that resembled the physical, real world, variants. For example, the calculator was designed as a pocket calculator, including the 3D buttons with gradients and shadows.
From iOS 7 on, Apple has completely switched to the flat style; gradients and shadows have been replaced by blocks without any effects and brighter colors. Also, many Apple apps were designed in a more minimalist way and therefore easier to use.
After Apple, many other companies have taken over the flat style and this style is now widely used, especially on websites.