Responsive design of website is more concessional for visitor so that new trend is responsiveness of website. responsive design is essential for web development company or web developer because every customer demand responsive design.
Responsive design mean website layout will change according to device screen size . if you are web developer then you can also check website design and responsive properties or if you are customer then you can also check you website property.
In General, For check website layout you must have different type of device and i hope this is not possible for every body but virtually you can check. there are lot of website where you can check.