In the original computer terminology, a directory is a path pointer to a file or group of files. That is, in fact, this is the path to the file, its address. For example, c: \ Windows \ is the directory of any file located in the Windows folder.

But in most cases, the term “directory” is used as a synonym for “folder” or “directory” - an object of a file system used to streamline file placement. 

In this context, the directory is a self-titled organizational element of the file system containing the names of files and subdirectories, as well as information about their properties.

A subdirectory is the same directory or folder, but placed inside another folder. So the concept of “daughter directory” appears, that is, placed inside a higher one level of nesting (mother) directory.

The concept of “root directory", that is, the original. It does not have its own name and is indicated by the "\" symbol (reverse slash) when it comes to the root directory on the hard drive. 

In the case of a website, the root directory is the one in which all the files and folders that make up it are stored. The “/” character (slash) usually matches it if you consider the relative file paths inside site.