Human-Computer Interaction (HCI) stands at the forefront of our interaction with digital technology, shaping the way we engage with computers, smartphones, and other devices. This research paper explores the historical development, theoretical foundations, and realworld applications of HCI, highlighting its pivotal role in enhancing user experiences and system efficiency. We delve into the theoretical frameworks underpinning HCI, examining its evolution from early usability studies to the modern user-centered design approach.