This text really is atrocious, isn't it? Jargon-ridden and very often unclear.
"Desktop deployment" is usually best interpreted as being "deployment (on)to desktops", i.e. implementing something on (a large number a) of individual workstations/PCs.

The "something" *could* be any application which is to be used by a number of users (hence the use fo the term deployment/roll-out.

Your "desktop application" would *usually* be taken to mean software such as a word processor, spreadsheets, dictionaries (for us!) - anything which is installed and used entirely locally and doesn't involve any interaction with a server or mainframe or anything else - if you disconnected the PC from any network (and took it home, say!), the application would still work.

So, you could have a desktop deployment of a desktop application (imagine a company that buys Word for the very first time) but the desktop deployment doesn't necessarily mean a desktop application - the application could be any software at all.