Skins are used to customize the look and feel of a wiki. The default skin we use is monobook, which is part of the standard Mediawiki distribution.
We have also installed the WPtouch skin, for mobile/tablet use. This is automatically selected for use when a mobile (eg. android, iPhone/iPad/iPod) device is detected.
You can explore alternate skins, and indeed choose another default for yourself (when logged in), by navigating to my preferences (located in the list across the top right of the wiki page), and then selecting the Skins tab to see and preview available skins.