CCS3 is an evolution from the CSS and improves the capacity to visualize web pages. It solves many of the traditional graphic effects which were performed with images, making loading faster and improving the crawling.
CCS3 describes how each HTML component has to be visualized (typeface, spaces, boxes, shadows, sizes…), and it is able to adapt this visualization for each device. It allows to visualize the same web page different for PC, for mobile, and even for a printer.
CSS3 is wide spread in the design domain and it does not requires high specialization to use.
Nowadays there are lots of open templates, like Bootstrap or Zurb Foundation, that allow to get professional designs in no time, even when the designer is not a professional.