Those look like Finder windows and if so, are just what files are stored in your "Documents" folder. Not categorized by macOS, just what you put into that folder. That "Documents" folder is yours to use any way you want. I see Music and Pictures and Movies, which, if you want to, can be moved to your Home folder (the one with your login name), but which will be just fine where they are if you don't want to do that move. "Documents" is a folder created for each user, under that user account name, for that user to put whatever they want. If you want to use a subfolder for what YOU think are documents, you could do that, give it any name you want and move what you think are "documents" into that folder. So you could have a folder named "Documents" inside the Documents folder, or you can call it "Word processing" or "Text files" or whatever you want. Or you could have folders for "Work," "Home," "Vacation," "Texas" or whatever you think you want to group together.
Now, if you ask Finder to find files where "Kind" is "Documents" it will include all sorts of things because it does consider as a "document" any file that does not fit into some other category like Application, System, Music, etc.
Apple has a document on Finder here:
https://support.apple.com/en-us/HT201732
EDIT: Follow some of the links in that article, too, to get more information on advanced uses. You can also check at Apple.com under Support and click on the spyglass icon and search for things like "Smart Folders" and "Searching" to see what Apple has published.