• Kernel - The kernel is the master control program of the computer. It resides in the computer's main memory and manages the computer's resources. The kernel also handles multitasking.
• Shell - The shell interprets the user's commands and passes them on to the kernel.
• File System - UNIX organizes information into files. Files can be grouped together into collections called directory files, or just directories. Directories in UNIX are similar to folders in Windows.
• Utilities - A utility is a useful software tool that is included as a standard part of the UNIX operating system. UNIX provides many utilities for things such as file management and text editing. Utilities are often called commands. From now on, utilities will be referred to as commands.

UNIX is primarily a text-based operating system. This means that it does not have a graphical user interface, or GUI. Windows, for example, is an operating system with a GUI. You interact with the OS by interacting with images (graphics) on the screen. (Clicking an icon for example.)

You will be working with UNIX as a text-based OS with no graphical user interface. In order to accomplish anything with UNIX you will have to type commands.