The essential parts that make up a desktop computer are:

• Computer case: The computer case is the metal or plastic box that contains all of the other components of the computer.
• Motherboard: The motherboard is the main circuit board in the computer. It connects all of the other components of the computer together and provides power to them.
• CPU (central processing unit): The CPU is the brain of the computer. It is responsible for carrying out the instructions of computer programs.
• RAM (random access memory): RAM is used to store data that is currently being used by the computer.
• Storage device: The storage device is used to store data that is not currently being used by the computer, such as operating systems, programs, and files.
• Power supply: The power supply provides power to all of the other components of the computer.

These are the essential parts that are needed to build a working desktop computer. However, there are a number of other components that are commonly used, such as:

• Graphics card: A graphics card is used to render graphics and display them on the monitor.
• Sound card: A sound card is used to generate and play sound.
• Network card: A network card allows the computer to connect to a network.
• Optical drive: An optical drive allows the computer to read and write CDs, DVDs, and Blu-ray discs.
• Monitor: The monitor is a device that displays images and text.
• Keyboard: The keyboard is a device that allows users to enter text and data into the computer.
• Mouse: The mouse is a device that allows users to control the cursor on the monitor and interact with programs and files.

These additional components are not essential for a working desktop computer, but they can add additional functionality and performance.