According to Murphie and Potts, “Medium theory is a special type of media study that focuses on such characteristics of each medium and on how each medium (or each type of media) physically, socially, psychologically distinct from other media.” (2002). There are 3 metaphors for this – media as conduit (textual analysis), media as languages (affordances) and media as environments (medium analysis).
An interesting way of explaining it was also described as hot and cold media – hot being information fed right to your brain say via a book, and cold media being something like TV – background noise, people choose to tune in and out to it. I thought this explanation was interesting and fed into media communication theories a little – with ‘hot’ being like the Bullet theory (in which media has a direct and instant influence on audience’s opinions) and ‘cold’ like the Users and Gratification theory (in which media does not influence an individual, and people consume media for their own entertainment and needs).