Wowza Media Cache is a caching mechanism that runs on Wowza Streaming Engine™ media server software. It’s designed for efficiently caching large video-on-demand (VOD) assets.
It can cache assets from various sources either through networked file systems or through regular HTTP requests to a web server or storage server. Some examples are in image below.
It can also be used with edge server DVR workflows to cache content from an origin server application that’s running Wowza nDVR.
Here is a video tutorial- you need to fast forward a bit to the Media Cache section.