*Contax-N lenses are the auto-focus/auto-aperture lenses and will only work on an EOS body if converted by Conurus. Originally designed for the Contax N SLR system.
*Contax-G lenses are auto focus rangefinder lenses. Not what we discuss here. Designed for the Contax-G rangefinder system.
*Contax-CY lenses are the manual focus/manual aperture lenses in the Contax/Yashica mount that are popular on EOS bodies with an adapter. Originally designed for the Contax RTS SLR system.
(All the above are discontinued.)
*Zeiss now makes ZE lenses, sort of a modern revamp of the former CY series in a native EOS mount. Not all are available yet. (Also made as ZF for Nikon, ZS for thread mount, and ZK for Pentax mount)
Biogon is the term Zeiss uses for their symmetrical wide angel lenses. Distagon is their retrofocus wide angle, designed for SLR type cameras. Needed to sit further away from the film plane due to the depth of an SLR's mirror box. Flektagon is a term used only by Carl Zeiss 'Jena', which was the company formed after WWII when Carl Zeiss was split in two. Carl Zeiss Jena lenses never really reached the same acclaim as Carl Zeiss in West Germany did.
for zeiss biogon vs. flektagon, etc.