Is BeagleBone Black a microcontroller or computer?
The BeagleBone Black is a single-board computer (SBC). 

It contains a AM335x ARM® Cortex-A8 which is a microprocessor (not microcontroller) with some peripherals, including two 32-bit 200&nbsp;MHz co-processors intended for real-time processing.  

The distinction between microcontroller and microprocessor is that the program memory and peripherals are typically external to the latter, though the distinction has faded somewhat in modern times as some processors have many peripherals on board and external memory buses which may or may not be used.