The Pico, just like the Arduino boards, is a microcontroller, and a tiny one at that. In fact, it's only slightly larger than Arduino's smallest board, the Nano, at 51 mm x 21 mm.

The Arduino Nano uses a bootloader for handling ... you can program the arduino chip over ICSP with the same circuitry as you use to reload a ... (7805 vs 1117 pinout, for ...

Both the Arduino Nano and Uno can be powered via their integrated USB connectors. This automatically supplies regulated 5V power to the board, allowing you to use any USB-supported power source ...

While the pinout is very similar to the Arduino Nano’s, there are four (12-bit) analogue inputs rather than eight (10-bit). Some digital GPIO pins are numbered differently too.

The Arduino Nano and Raspberry Pi Pico support different input voltages, so they also use different power sources. However, they can both be powered with a 5V supply via their onboard USB ports.