A binary logical input can only tell whether the voltage (electrical potential) at a pin is below a threshold or above a (usually different) threshold. An analog input can, to an extent, report the actual voltage at a pin.
Analog input pins are limited by two main factors: resolution and speed of conversion. Most analog-to-digital converters (ADCs) have at least 8 to 10 bits of resolution. This means that the entire range of safe input voltage is divided into 256 or 1024 values. High resolution ADCs can have resolutions up to 16 to 20 bits.
Applications