Arduino is not alone in the universe; it can use different digital communication protocols to talk with quite a few other systems. It's one of the great features of the platform; it has all of the standard protocols built in, allowing it to communicate with thousands of different devices.

Digital communication has numerous advantages. It is less susceptible to noise than analog communication, and it usually only requires two lines to communicate to hundreds of devices. This allows communication with the computer, with other microcontrollers such as the Arduino, with the Internet, and even pages to store data.