Concepts

+-------------------------------+
|          Linux System         |
+-------------------------------+
| - Init system: systemd/sysv   |   ← SysV vs BSD init style
| - ps command: BSD/SysV flavor |
| - Filesystem layout: FHS      |
| - Desktop: GNOME/KDE/etc.     |
| - XDG tools: xdg-open, etc.   |   ← XDG layer (optional)
+-------------------------------+