This document provides an overview of signals and systems. It defines a signal as a pattern of variation that carries information over time. Signals can be continuous or discrete. Systems process input signals to produce output signals. A system can be represented as the ratio between its output and input signals. Examples of systems include electrical circuits and communication systems. Properties like linearity, time-invariance, and causality define important classes of systems. Key signal types include periodic, exponential, step, and pulse signals. Continuous systems are often modeled with differential equations while discrete systems use difference equations.