This chapter provides a comprehensive overview of antennas and their diverse applications across modern communication and sensing systems. Beginning with the history of evolution of antenna and fundamental principles of antenna theory, various types of antennas are examined with attention to their operational characteristics and suitability for specific technologies. This chapter delves into practical design considerations that influence antenna performance in real-world scenarios. A wide range of applications is discussed, spanning wireless communication, medical systems, radar, defense and aerospace, and emerging Internet of Things (IoT) networks. By integrating theoretical insights with practical implementation strategies, this chapter serves as a foundational reference for students, researchers, and engineers involved in antenna design and deployment.