Processor (Central Processing Unit, CPU) - this is an electronic unit that executes machine instructions and is the head of the hardware component of a computer.
The processor can be designated as chip, located on the motherboard by connecting to a special connector or directly unsoldered on the board.
Today the processor is an integral part of any personal computer or mobile device.
For an ordinary user, the processor is of no interest without additional devices that provide power to the device (power supply), data storage (hard disk, memory drives), data input (mouse and keyboard, touch screen), data output (monitor) and so on.
Based on this definition, we can conclude that the processor differs from the computer (system unit) in a smaller breadth of the concept and the presence of an independent functional component.
Computer (system unit) - physical platform for creating a computer machine.
Simply put, the system unit is called metal box, in which the computer components are located. Organic glass, plastic, wood and so on can also be used for modding purposes.
The system unit without the computer components is called case.
By citing the simple the difference between the computer and the processor, we can emphasize the fact that the processor is just included "stuffing" of the complete computer.
If it comes to a conversation that a computer is required to repair or install software, then it is true to use the term "computer (system unit)", and not "processor".