Microprocessors

Please can someone tell me the differences between a microprocessor and microcontroller?

Microprocessor:
A microprocessor incorporates most or all of the functions of a central processing unit (CPU) on a single integrated circuit (IC). That is, it has Logic and arithmetic units. But alone, the microprocessor is nothing. It has to be interconnected with other devices (I/O ports, Memory devices etc) for it to functionbut it still forms the heart of the entire control process.
The microprocessor can not be referred to as a computer but it does form the heart of one.

Microcontroller:
A microcontroller is by definition, a computer on a chip. It includes all the necessary parts (including the memory) all in one IC. You just need to apply the power (and possibly clock signal) to that device and it starts executing the program programmed into it. A microcontroller generally has the main CPU core, ROM/EPROM/EEPROM/FLASH, RAM and some accessory functions (like timers and I/O controllers) all intergated into one chip. The original idea behind the microcontroller was to limit the capabilities of the CPU itself, allowing a complete computer (memory, I/O, interrupts, etc) to fit on the available silicon real estate.

Microcontrollers are typically used where processing power isn't so important. More important are generally compact construction, small size, low power consumption and that those chips are cheap. For example controlling a microwave oven is easily accomplished with the smallest of microcontrollers. There are countless number of small electronic devices which are nowadays based on microcontroller. A modern home can include easily tens or hundreds of microcontrollers, as almost every modern device which has electronics has a microcontroller (or more than one) inside.

Final Word:
A microncontroller is a "complete computer" that has a microprocessor(CPU), I/O Devices, memory and other peripherals all on a single chip, while the microprocessor is the heart of it : it still needs other devices to be interconnected for it to function. A microncontroller, in features and possibilities, is a stripped down version of a microprocessor.

You can read more about them here:
Microprocessor
Microcontroller