jai,
A microprocessor is what is in a computer (Central Processing Unit or CPU). I think you mean a microcontroller. A microcontroller runs a small program. You will find many peripherals attached to a computer with microcontrollers communicating back and forth with the microprocessor. They free up many of the small tasks that would slow down a microprocessor in the computer. The microcontrollers usually have a much more restricted instruction set.
MP