I/O

Input/Output. I/O usually refers to the capability of a pin on a microcontroller of being able to both send and receive information (a data signal).

Input can be either an analog (commonly a voltage between 0 and 5 volts (or 3.3 v) ) signal or a digital signal (0 volts or 5 volts (3.3 volts)). To process an analog input, an analog to digital converter (ADC) is required. Thankfully, many micro controllers include this.

Output can also either be a digital signal (0 or 5/3.3v) or an analog signal which is created by using Pulse Width Modulation (PWM).