micro controllers are used often for embedded applications, due to the fact that they have most everything on chip, (RAM, ROM). They are also much cheaper to mass produce so if for example you needed to put a chip in a appliance for one application it would probably be cheaper to use a micro controller. Someone had said that there are less operations you can do with a micro processor, which is wrong, the number of instructions in the instruction set of a micro processor will far out number those of a micro controller. Most microprocessors are also 32 bit which allows for much better arithmetic operations, the instructions will compute addition of two 32 bit numbers in one line of code rather than an 8 or 16 bit micro controller which may require you to use multiple instructions to make sure your addition of two numbers will be correct.