Do you know what a CSS Framework is? Are you aware of the different CSS Frameworks that are available to you?
Everyone nowadays in the development community of CMS is talking about responsive design, having a theme/template that is responsive allows your website to show up on any size of screens from your laptop to your smartphone, without the need to build a mobile app.
There are many ways you can go about creating a responsive design, the article Best Responsive CSS Frameworks for Web Design is a good read to get you started.
Myself I use the Bootstrap framework for any web development I’m doing, it is a very clean responsive framework that can be used for any type of web site, there are plenty of developers that are using it in developing themes/templates.