Explore the fundamentals of conversational AI in this 12-minute lecture from NPTEL-NOC IITM that examines the intersection of Human-Computer Interaction (HCI) and Natural Language Processing (NLP). Learn how HCI principles inform the design of AI interactions, understand the core concepts of NLP, and discover the differences between rule-based and data-driven dialogue systems. Gain insights into designing user-friendly voice assistants while addressing challenges in context awareness and personalization. The lecture covers practical applications in healthcare, education, and customer service, while also addressing important ethical considerations in the development and deployment of conversational AI technologies.