When using a versioning system, it's often practical only to include those files that are required for the project, while files containing user-specific settings (such as IDE layout) are kept outside the repository.

As far as I can see, the file formats of the IDE are as follows:

PPW Workspaces; contains a list of the projects and of the expanded nodes of each project (a mix of user-specific settings and required settings).

PPJ Project files, contains project settings, such as include paths, hidden file patterns and which file to execute.

There are a number of files which I'm not at all sure what do, and which would have been very helpful to know a little more about. These are:

PPD Appears to contain IDE layout for the profiler (in which case it would be a user-specific file)

DSK List of open files, breakpoints and cursor locations (also entirely user-specific). However, DSK also appears to contain parameters for debugging runs, which could be of use for other members of the team.

All the files are used by the IDE.

ppd - profiler data. It saves all the sessions if enabled. See Tools->settings->debugger tab, "Save profiler history" and "Keep profiler sessions".
If you open profiler window, you can list stored data with right and left arrows.
Phped creates ppd files for each workspace.

dsk - contains workspace's desktop, in particular the files opened, cursor locations, breakpoints, watches and arguments
Phped creates dsk files for each workspace.

ppx - contains structures shown in the code explorer window.
Phped creates ppx files for each project.