Responsive websites are designed to be viewed in a range of conditions and on all sorts of devices, from laptops to desktops to phones and tablets. Responsive is an important word in web design, meaning a website can be displayed as best it can within the size of the device it is seen on. It can even adapt for screen size, resolution, speed and bandwidth limits, as well as the method of interaction and physical orientation.
Responsive design is all about prioity. All websites have a lot more content than can be displayed on a single screen, so each website needs to choose the most important bits to show at any given time. The home page will show the information the visitor needs to see first.
Responsive sites need to be even more careful when it comes to prioritising, as visitors often have limited time and space because of the device they are using. As the website is limited down, what it displays is reduced, pushing away less important information and leaving the juicy bits in.