I found this really great article that talks in depth as well in an easy language about the new options of under look and feel of 2013.
here are the basic points:
· Design Manager is a web-based tool that you can use to create your own SharePoint site designs. The tool is wizard based and walks you through uploading design files, editing your master page, changing page layouts, and publishing and packaging your design.
· Device Channels enables you to specify certain characteristics of your site based on the device used to view the site. A channel can be optimized for the device to display the site in a specific way.
For example, you can set up a channel for smartphones (such as an iPhone or Windows Phone). You could set up a different channel for the iPad or Surface tablets. And finally, you can set up a channel for laptops and desktop browsers.
· Import Design Package enables you to import a design package developed by a third party or in-house designer.
· Navigation enables you to manage navigation links and also change how the navigation behaves. You can configure global navigation (top of page) and also current navigation (left side of page). The Navigation settings page also enables you to change the sorting order of the navigational links and show and hide the Ribbon.
to see the entire article check out the link at :