Hearing Aid is a non-surgical electronic device to help individual with hearing loss. It has mainly 3 components Microphone, Amplifier and Receiver.
Analog hearing aids basically take sounds from environment and make them louder. Some analog hearing aids include a programmable microchip, but the functions are relatively basic. Becoming less common due to technological advancements.
Digital hearing aids obtain environmental sounds, convert it into digital format, process, filter, amplify and deliver a sound signal into ear that is customized based on needs. This is called Digital Signal Processing (DSP) via a microchip.