"Responsive Design" is the new buzzword that you hear plastered all over the web. What exactly does it mean?
With the advent of mobile devices, it became obvious that web sites had to be usable on mobile devices. There is nothing worse than trying to do the "pinch and zoom" move on a small phone so that you can read a web page that is designed only for large laptops.
There are a lot of services that offer separate websites that come up when you are accessing a site on a mobile device. The problem with these services is that a separate site has separate content! It is a nightmare to keep the two separate sites in sync!
So, crafty designers came up with the concept of "Responsive Design". When a responsive site is viewed on a smaller device, the site automatically adjusts to fit in the smaller device in a way which is READABLE.
I only use responsive tools and software when building my client sites.