This chapter provides an overview of communication systems and their similarities to radar systems. It demonstrates that much of the top level system components of either system are similar in form and function. The intent is to introduce a bird's-eye view discussion of both systems that is commensurable with causal and non-expert readers interested in learning more about radar systems. In general, radar systems use modulated waveforms and directive antennas to transmit electromagnetic energy into a specific volume in space to search for targets. Clutter is a term used to describe radar returns from any object that may generate unwanted radar returns that may interfere with normal radar operations. The radar receiver demodulates the radar echo signal so that the signal processor can extract target relevant information from the returned signal. In this case, the radar receiver knows exactly the nature of the transmitted signal.