Despite their similar sizes and affordable prices, microcontrollers and single-board computers have vastly different specifications and use cases. After all, MCUs are designed for circuitry, ...
Arduino is a network for open-source electronics focused on a technology that is easy to use. By giving a list of instructions to the microcontroller on the board, you can tell your board what to do.
When it comes to performance, there's a world of difference between the Raspberry Pi and Arduino. The former, after all, is technically a fully functional computer that can run games, word processors, ...
So you've already outgrown Arduino's most beginner-friendly board, the Uno, and are looking to move on to bigger, more exciting projects. In that case, the Nano family might just be what you need.