The microcontroller is a controller that runs the code (software) you write. The controller is embedded in a chip and this chip is put on a PCB. A raspberry pi is a single board computer, It has all the interfaces (USB for input devices, HDMI out for video out and ethernet for connectivity) needed for a computer on one board (PCB). The microcontroller is in this case an ARM processor inside a chip from Broadcom on that raspberry pi board.
Hardware and software advisor for tech startups. ASIC, FPGA, RPi, Arduino, AI, robots, drones, blockchain, Machine learning, vision processing, IoT and 3D printers are my fields of expertise.