The frequency response is an extremely insightful description for linear time invariant (LTI) systems. The output of a LTI system at a given frequency is simply the product of the input at that frequency and the frequency response. In this lesson you will learn the relationship between the frequency response, impulse response, differential equation, and system function descriptions for discrete-time LTI systems. Each of these different ways of describing the input-output behavior of LTI systems provides a unique perspective on the system characteristics. Developing your skill at relating these different descriptions will be extremely beneficial to your practice of signal processing and provide you with a comprehensive view of system behavior.