Mid Century usually implies the post-war design period from 1945-1969. If you watched ‘Madmen’ you already know this style very well. Sleek lines, sometimes geometric and sometimes naturalistic but always minimal.
Form follows function, all design details have a purpose. New materials were used like Aluminum and polymers – often with intense and clashing colors and textures. There is rarely any decoration and what there is typically abstract and/or minimal.