The following directory structure (also called folder structure or directory tree) is usually found on every standard installation of Unix and Linux. This directory structure also resembles the structure of macOS. Except for Multics, which is the predecessor of Unix, Unix is the mother of the operating systems.
Directory Structure
Root Directory
Binary Files for All
Contains the binaries of the system commands, these programs can be executed by all users.
Files to Boot Up
Hardware Connections
Et Cetera
Working Environment
Libraries - Kernel Modules
Mount
Optional Programmes
Commercial or optional programs with their own libraries that do not directly belong to the system are stored in this directory.
Pseudo File System
System Administrator
This is the home directory of the system administrator (root user). For security reasons, this directory is not in the home directory of the usual users, and for the same reasons, the root user should only be used for maintenance work.
Binary Files for Superuser
Binary files for necessary system commands are located in this directory. Commands can only be executed with root privileges or superuser privileges.
Device Information
Temporary Files
User System Resources
User
Header Files
Library
Structure like usr
Optional
Optional system commands and system utilities.
Miscellaneous
The Source
Variable Data
Fluctuating data and directories that are created during the processing of programs.
Cache Memory
Information Status
Variable status information, these change during runtime.
From /usr/local
Variable data related to installed programs from the directory /usr/local.
Prevent Data Loss
Important Information
The log files are generally located here.
From /opt
Storage for variable data related to programs from the directory /opt.
Running Processes
Directory for files of running processes like process identifier (PID).
Waiting Queue
The files for queued processes are located in this area, including print jobs and email sending jobs.