The design responsive is focused towards an improved interface for web browsing on mobile devices. The main objective of this type of design, is to improve the appearance of the websites with respect to the type of device with which the user is accessing. This kind of design uses code HTML5, CSS3 and Media Queries.

The HTML5 code is new, it is the fifth version of the basic language of the World Wide Web, this version was released in October 2014. In this code new tags are added, highlighting among them:

<section>  </section>
<header>  </header>
<footer>   </footer>
<video>  </video>
<nav>  </nav>

Media Queries belongs to CSS3 and defines in different ways the design of a responsive site.
With the use of Media Queries, a website can be adapted to different types of devices, such as mobile device screens.
The Media Queries are conditions used in CSS3 that modify the design of the website using different types of criteria. Example:

@media screen and (min-width: 560px){...}

The use of these two languages has increased considerably in recent years, and are now being used by recognized websites.

And what do you think?