A microprocessor, oftentimes simply referred to as a processor, is a device that contains only a CPU on the chip. These are discrete parts that are combined with memory, a clock and storage to make a computer. A microcontroller, on the other hand, is a compete computer in and of itself. It has the clock, the CPU, the memory and the permanent storage—ROM—built into a single device. A microprocessor is part of a computer; a microcontroller is a computer.