When several people are together they usually elect, select or appoint a person to lead or coordinate them. For example: A school has several people; teachers, students, non-teaching staff. To coordinate these people, a principal is appointed.
Computer follows the analogy where several components performing different tasks are brought together to form a computer. For instance a desktop computer basically has a keyboard, mouse, monitor and motherboard(Located inside System unit), CPU, Memory among others.
Have a look at this picture below

As the principal coordinates school, a computer also needs a device to coordinate components forming it. A computer has device known as Central Processing Unit (CPU) or Processor. This device coordinates all functions of the CPU.
Our Lesson today will focus on CPU.