This chapter covers the fundamental concepts of signals and systems, essential for applications across engineering and applied sciences. It begins by exploring various signal types and examples to build a solid understanding of signal behaviors and properties. Key signal types discussed include sinusoids, exponential and geometric signals, and standard functions like the box, Kronecker delta, Heaviside step, signum, sinc, Bessel, and Gaussian functions. The chapter then shifts focus to systems, examining critical properties such as linearity, time-invariance, causality, stability, and memory, which are essential for analyzing and predicting system behavior in signal processing. Finally, it addresses noise, an unavoidable element in real-world signals, and its impact on signal integrity and system performance.