Arduino is an open-source hardware and software company, project and user community that designs and manufactures single-board microcontrollers and microcontroller kits for building digital devices.
Arduino Nano is based on the ATmega328 SMD chip. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 8 analog inputs, 1 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, and a reset button.
The Arduino Mega can be powered via the USB connection or with an external power supply. The power source is selected automatically.