Baffled by Libraries/Documents

My user directory (C:\Users\<username>) contains lots of directories and files. However if I look in Libraries/Documents, I only see a small subset of those.

What is going on and how can they be reconciled?

Thanks
David

I just switch Off Libraries, too confusing.
In File Explorer
The Show Libraries On/Off option > 3 dots > Options > View Tab, towards the bottom.

I'm with you. @Helmut I don't do libraries either and haven't for years. I have my file explorer tweaked to leave me with the simplest, cleanest interface possible. It opens to "this PC" with only user folders pinned to the top left navigation pane and disks in the right pane.
The bottom left navigation pane also has my drives. The biggie for me was to disable the expand to open folder option in the bottom left navigation pane.
It nearly drove me nuts when I was dealing with multiple drives..
No recents, onedrive, or suggested. Oh, and the modern context menu. I kicked that sucker to the curb on day 1.