This course will teach you how to create responsive web designs using CSS. You will learn how to use media queries, flexbox, and other CSS techniques to create websites that look great on any device. You will also learn how to use responsive frameworks such as Bootstrap and Foundation to quickly
From Wikipedia
Responsive web design (RWD) or responsive design is an approach to web design that aims to make web pages render well on a variety of devices and window or screen sizes from minimum to maximum display size to ensure usability and satisfaction.