In my installation of MediaWiki, it says:
Warning: Can not find APCu, XCache or WinCache.
Object caching has not been enabled.
Links: APCu is http://www.php.net/apcu XCache is http://xcache.lighttpd.net/ WinCache is https://www.iis.net/downloads/microsoft/wincache-extension
Questions: What is the purpose of these resources? Should I install in which folder? How should I install it?