Responsive web design is a methodology where the application's UI automatically fit with the view port or the device screen with the same code. There are several types of device like large desktop, medium desktop, tablet, phablet, mobile, TV and what not. I came across many issues and challenges to create responsive nature of a web application which really run well in across devices.
For more details please visit - https://lazypandatech.com/blog/Miscellaneous/21/Simple-way-to-design-Responsive-Website