A signal is a function that gives information about a phenomenon. The field of electrical engineering that studies output and input signals, and mathematical representations between systems is known as signals and systems. The four main domains of signals and systems are frequency, time, s and z. It is a subset of mathematical modeling. Signal processing involves analyzing, synthesizing and modifying signals. Its techniques are used to improve efficiency and subjective quality, and transmission. It receives signals as well as produces them. System is a physical set of components. It has one or more input and output signals. In signals and systems, signals are classified according to many criteria. Different types of signals include analog, digital, deterministic, random, energy, power, etc. The book aims to shed light on some of the unexplored aspects of signals and systems. Such selected concepts that redefine the subject have been presented in it. For all those who are interested in signals and systems, this book can prove to be an essential guide.