Biological systems exhibit a remarkable complexity, characterized by intricate networks of molecular interactions that underlie the processes of life. Understanding these networks has become a cornerstone of modern biology, shedding light on the organization, dynamics, and function of living organisms. This review serves as an introduction to biological networks, providing an overview of their types, structures, and functions. We explore various types of biological networks, including metabolic networks, gene regulatory networks, protein-protein interaction networks, and signaling networks, highlighting their distinct characteristics and roles within the cell. Additionally, we discuss fundamental principles of network analysis, such as network topology, modularity, and dynamics, which are essential for unraveling the complexity of biological systems. Furthermore, we examine the applications of biological network analysis in diverse fields, including systems biology, medicine, and biotechnology. By synthesizing foundational knowledge from network science and biology, this review aims to provide researchers, students, and enthusiasts with a comprehensive understanding of biological networks and their significance in modern biological research.