Why can't create folders and files without root privileges in Linux?

Question

linux

Yesterday I installed WordPress in the root of the site folder on my computer at /var/www/html/site_name. I
created a mysql user with all privileges, created a database for the project, and specified all this when installing WordPress.
After that (perhaps this is not the reason) I cannot create folders and files not only inside WordPress, but also inside the entire file system. But, if you open the folder by specifying open as root , the outside options are available again.
However, when I save changes to the site files in the editor, a window pops up every time asking for a password.
Help plz.

Answer 1

Probably because all files outside the homework belong to the root :) Including /var/www/html. By the way "created the user" - where? in mysql db? Well, it has nothing to do with system users. You need to create it in the system, and then give permission to the directory in which you need to write
man chmod, man chown

Answer 2

ls -l do and see what you have for the rights to the directories and what kind of owner