Responsive Web Design refers to what happens when you resize your screen. The content of the page resizes to fit the window. You see, screen sizes differ, when we look at the screen on our computer at full size compared to our tablet or phone at half size we WANT to see the same content that is easy to read and easy to manipulate like big buttons for our fingers on our phone, or half size the screen on the computer for multitaksing.
Designers and web developers should utilize Responsive Web Design becuase todays technology is forever changing. Bigger screens, smaller screens, with way a gteat website should be legiable to the viewer no matter what device they might have.
Personally my process starts with sketching. I do it by hand or in this case I used Photoshop. Bascially I draw up what I want the site to look like on a small screen and then what it should look like when it is expanded. I learned that it is easier to start small and to work up. Once I get the content up on the site I then find breakpoints. Which is the point at which the website changes its view.