CSS3 is the most recent version of the cascading style sheets language. It is the language that is used to define the appearance of the HTML elements. As design and web is evolving constantly, so did the languages, and CSS3 has the aim to make element styling easier. It can commonly be used with preprocessors such as LESS, SASS or SCSS.
CSS3 provides a variety of features that aim to make styling easier with less code, such as rounded corners, box-shadows, 2D or 3D transformations and other. With the use of preprocessors the styling job gets easier has it is possible to nest elements, create mixins, create variables and inline import other stylesheets.