This introductory lecture from Yale's Introduction to Medical Software lays the groundwork for the course by defining what medical software is and outlining the scope of the field students will study. The instructor introduces the range of software types covered, from clinical decision support and electronic health records to standalone diagnostic applications, and explains why medical software occupies a distinct regulatory and engineering category compared to general consumer software. The lecture previews the course's structure, which spans regulation, risk, lifecycle management, and data security, giving students a roadmap for the technical and compliance topics ahead. It is aimed at students with an interest in software engineering or health technology who want a grounded introduction to how software is built and governed in a medical context.