Topic on User talk:Garrett
I see I somehow lost the mention of terminology while rewriting before I posted. Expack3's response covers some of the technical specifics, but you'll often see sites use the two terms interchangeably to refer to the same method. Both Nvidia and AMD seem to only use "downsampling" to describe Super Resolution.
The Glossary: namespace has no special behaviour. The main purpose of the additional namespaces was to move non-game pages out of the main namespace.