you could find the definition in the server reference manual.
A user document is the document that an end user sees when accessing a document on QlikView Server (QVS). To fully identify a user document, both the QVS server/cluster and the path relative to the server have to be known. Technically, a user document consists of three files:
1. .qvw file that contains the data and layout.
2. .META file that contains:
a. AccessPoint attributes
b. Pre-load options
c. Authorization (Document Metadata Service – that is, DMS – mode only)
3. .Shared file (see below)
Note! If the user document is distributed by the QlikView Distribution Service, both the .qvw and the data in the .META file are overwritten.
The access to user documents is controlled by QlikView Server.
Source documents are only applicable when a Publisher license is applied. Most source documents originate from a developer, others are created by the QlikView Distribution Service as part of the distribution process. QlikView Data files (QVD) can also be created as part of the distribution process as an intermediate step. A QVD file is a table of data stored in format that is optimized for speed when read by QlikView.
The access to source documents is governed by NTFS.