Responsive design is a website design practice, in which, the layout of the website varies according to the screen width of the device used to access that website.
It can be considered a “one-size-fits-all” solution as it is generally used to design one version of a website (e.g., for mobile) and then scale it based on the device used to access the website.
Responsive design, when done properly, results in the website layout smoothly adjusting to the browser width, no matter what device is used.
Responsive design uses one template and varies the website layout for different browser widths.
Responsive design is similar to Adaptive design in that the website’s layout (and subsequently page assets) changes based on the viewport; however, where this design philosophy differs is that it modifies the existing layout depending on the user’s viewport.