Today, when using the term: "responsive design", you are most likely thinking about using media queries to change layout when resizing a design from mobile size, to tablet size, through to desktop size.
But soon, this perception of responsive design may be considered as outdated as using tables for page layout.
Viewport-based media queries give you some powerful tools, but lack a lot of finesse. They lack the ability to respond to user needs, and the ability to inject responsive styles into components themselves.