HyperText refers to inter-related texts which are hyper-linked. So a webpage with Info A can link to Info B through a hyper linked text within it. (Whats done by anchor tags in HTML page)
Now the Text and webpages are transferred through HTTP , the Hyper Text Transfer Protocol. Now, a webpage or a web content or HTML page that you see is not necessarily made just of texts and inter-related text content. We deal with content which are mostly of type “Media” , meaning an audio, video or a visually augmented content. These type of content in turn lead us to related content by just click in parts of these content (Say a 3d view changing as per user perspective changes).
Now these types of content prevalent now, which includes just not inter-related content but inter-related media content are referred to as Hyper Media.
Strangely enough most of the webpages still transfer media content through the HTTP ! ( eg, HLS / HDS/ MPEG DASH Streams! )