What is MCU, what role?

What is MCU, what role?
http://www.siliconray.com/catalogsearch/result/?q=mcu
This is an interesting question, because who have not provided a who approved by all concept, that exactly what is single chip? Single-chip microcomputer and says monolithic micro controller, it is not a complete a logical function chips, but put a computer system integration to a chip. Summary of speak: a chip became a computer, in fact this concept is not approved, an example is DSP, ARM, why don't you call a single chip processor? Ha ha, there is no need to find clear concept to analyze what is a single-chip microcomputer, to understand it, literally get kind of SCM (single chip microcomputer 8051 is the best) to have a small project, you will know what is the microcontroller.
Now of course colleges and universities, as long as professional and electricity related, cannot leave the single-chip microcomputer course