Norton folder contains these files. What does each of them mean?

Desktop shows a short cut to a Norton folder, within Shared Documents.
This folder contains some files:

What exactly does each of these mean?

 

--------listing of files in Norton folder---------

2012Plugin.dll, 168 kb, application extension
2013Plugin.dll, 265 kb, application extension
downloadinfo.txt, 1 kb, text document
NIS-UPGRADE-ESD-NoDefs-20-1-1-2-EN.exe, 45338 kb, application
setup[1].exe, 895 kb, application
symcdefs.exe, 97556 kb, application