In practical terms, those numbers mean that if your website isn’t optimized for mobile devices, you may be missing out on a significant number of users. With so much content out there, your potential audience (and customers) aren’t likely to put up with a poor user experience. They’re bound to look elsewhere for what they want.

What Does Responsive Web Design Mean?

Responsive design means that no matter how big a screen is, a site will fill it properly and present information in a clear way. This can be on a phone, tablet, desktop, or even a smartwatch.

When you browse a website, you should notice that it adapts to the size of your screen. For large screens, elements will scale up to a point, so they don’t look oversized, but they remain easy to engage with.

The same happens with mobile devices. When you’re using a smaller screen, you want the content of your site to scale down, but not so much that it becomes unreadable or impossible to interact with.

Websites that can pull off that delicate balance are considered responsive. Web design and development go hand in hand here, as the site’s graphical assets need to scale. In the background, there’s CSS and stylesheets that govern how the website will display across different size screens.

Until recently, responsive design was an afterthought. We used to design websites all around the desktop experience. Now that mobile traffic comes first, so does mobile design. That’s why you’ll often hear the term ‘mobile-first’ in web design circles.

It’s important to understand there’s a difference between responsive and adaptive design. Adaptive design involves creating multiple versions of a single page and serving them depending on what type of devices visitors use. That approach to web design is considered outdated nowadays, as responsiveness is the more efficient option.

Source Dreamhost.com