Responsive [rɪˈspɑːn.sɪv]: in general a term for websites which change their layout depending on the screen size of the device the website is visited.
The term emerged when more people used their phones and thus smaller screen to surf the web. In responsive design the layout of a website is not fixed, but is dynamically changing depending on your screen size to give the best experience across all devices. CSS3 –the newest version of the web’s styling language– added many features to enhance responsive design.