These are all server files, usually located in the same subdirectory as your published documents:
.pgo Server objects like CAL information, Ticket information etc. Managed by QVS and not really intended to be used or manipulated by developers. HOWEVER, some can also be exported as xml and then read by a suitable QVW. Ex. look for the License Analyser in the resource Library.
.meta (one per document) contains all sorts of settings that relate to this document and were done in the QMC (like AP settings, load options, DMS settings etc.) No sure if you can read these.
.shared (one per document) contains this documents shared objects and their properties (like ownership and such) QlikView Power Tools has some basic tools to view and change the contents of these files
Look in the QLikView Server Reference manual for more details.
This are proprietary file-formats from qv. Unfortunately there aren't a official documentations and only a few infos in the community.
Shared files contains user-objects like bookmarks - in the power tools is are vievwer available.
PGO-files contains current data about the user-access - you could put "PGOAsXmlAlso=1" in the settings.ini from server to receive these files additionally as readable xml-files.
Meta-files contains data about which user/usergroups have access, in which category belonged this app,some more - you could read these files with a hex-editor - perhaps there are also viever in the power tools.