Responsive and Adaptive Design
Many people are mixing this two different aspects. The first step is to have a common understanding of this approaches.
Responsive Design
Responsive designs respond to changes in browser width by adjusting the placement of design elements to fit in the available space.
A responsive application shows content based on the available space. If you open a responsive screen on the desktop and then change the size of the window, the content will move dynamically to arrange itself (at least in theory) optimally for the screen.
Adaptive Design
Where responsive design relies on changing the design pattern to fit the real estate available to it, adaptive design has multiple fixed layout sizes. When the site detects the available space, it selects the layout most appropriate for the screen. So, when you open a browser on the desktop, the site chooses the best layout for that desktop screen; resizing the screen has no impact on the design.