Given the huge range of capabilities, available tools, library of third-party applications, and size of the community, this lecture covers a basic introduction to GNU Radio. We will explore, through some historical context, the use of GNU Radio to build some simple applications. Although simple, a key to using GNU Radio is through exploration of the tools and available features, and so the introductory material is meant to overcome the basic difficulties of just getting to know what GNU Radio is and what it can do. With this knowledge that provides an exposure to the library, webpages, tools, and community, we think that other users can continue to explore the space of capabilities and applications for much more advanced features.