To use it as such, you need a USB cable and a 5V power source. In the case of the Arduino Nano, a mini-B USB cable is required. The power source, on the other hand, can be a powerbank, a phone ...

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 ...

“The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 ... It lacks only a DC power jack, and works with a Mini-B USB cable instead of a standard one. ...