MediaWiki is probably best known through it’s use as software driving WikiPedia, the on line, collaborative ‘encyclopedia’. It is in fact a content management system, but focused very much on knowledge content and interlinking between bits of knowledge and less on flashy presentation with lots of images.
There are various other implementation of the concepts of a ‘wiki’, such as Dokuwiki, some of which either use different underlying programming languages or don’t use an SQL back-end to store information in. If you are already running a xAMPP (Apache or Nginx server, MySQL or MariaDB database, PHP and Perl) stack anyway, there really is no reason why you would have to look into some of the other ‘wiki’ implementations, would not simply download and install MediaWiki, if you need a knowledge focused intra-net or Internet site.
MediaWiki can be expanded with extensions and there are some different themes, but much less than for the usual content management systems such as WordPress, Drupal or Joomla. 
This clearly reflects the focus of and philosophy behind the ‘wiki’, a rather blank sheet of paper (themes tend to be light colored) on which you and other collect information about topics of interest (knowledge) with proper references (scientific and well documented). Thus it really is more like a good encyclopedia or scientific journal than an image loaded and flashy effects driven social media site.
You can find more information and download MediaWiki here: https://www.mediawiki.org/wiki/MediaWiki
You undoubtedly already have the link to Wikipedia in your favorites (and hopefully have donated a little bit of physical or financial support):
https://en.wikipedia.org/wiki/Main_Page
Dokuwiki: https://www.dokuwiki.org/dokuwiki#