Arduino is an open-source electronics platform based on easy-to-use hardware and software. Arduino boards are able to read inputs  light on a sensor, a finger on a button, or a Twitter message and turn it into an output activating a motor, turning on an LED, publishing something online. Arduino functions allow structuring the programs in segments of code to perform individual tasks. The typical case for creating a function is when one needs to perform the same action multiple times in a program.