ELI5: Explain Like I'm 5

Infinite impulse response

Infinite Impulse Response (or IIR) is a system or process that produces an output when it is given an input. It remembers the past inputs it has been given and uses them to create the output. It’s like a robot with a memory that can repeat a pattern it learned. IIR is used in many different kinds of things, like electrical circuits, computer programs, and sound systems.