What files does Windows 10 “Reset this PC” keep?

Windows 10 includes an option to Reset this PC which can be accessed in Settings → Update and Security → Recovery.

When you choose to reset, you’re given some options:

The “Keep my files” option says it “keeps your personal files”, but which files does it actually keep?  Personal files could mean files in my Windows user folder, or it could just mean the Documents, Pictures, Music, and Videos folders, or it could mean everything that’s not Windows.

Sometimes I need folders without spaces in the path, so I store (important) files directly in the C drive.  Are these saved as “personal files”?

Although I have backups, I’d prefer not to have to use them.

For the purposes of Windows 10 reset, what are considered personal files?

Solution:

Since I could not find the information I was looking for, I did a reset and performed an experiment of my own.  I put TEST.txt files in various directories beforehand to see which remained after the reset.  The results were mostly what I expected, except files saved to the system drive by the user did remain (even though they weren’t in the user profile).

NOTE: Files that are not saved are moved to the C:Windows.old directory.  You can recover files from this directory after the reset.  (thanks @LPChip!)

Here’s what is and is not saved:

• Files in your user profile folder (C:UsersYourName) are saved as expected.  It doesn’t have to be in a sub-folder (Documents, Pictures, etc) as files saved directly in the profile folder are saved as well.
• Files in the system drive are saved.  That is, files in C: (if C is your system drive) and sub-folders that you created there are safe.
• Despite being in your user profile, AppData is wiped (C:UsersYourNameAppData).  Files there are NOT saved.
• Files in Program Files, Program Files (x86), ProgramData, and Windows are NOT saved.  This is expected because Windows says "apps" are removed.  Windows will make a list of programs removed and put it on the Desktop for you after the reset.
• Files stored directly in the users folder (C:Users) and not in a specific user profile are NOT saved.
• The Public user profile (C:UsersPublic) is NOT saved.

I believe this information is not present elsewhere on this site, and hope that it may be useful to others who are contemplating using the Windows 10 reset feature.