Meta­data in various forms pervades our institutions, technologies, and daily lives. Meta­data is a distinct focus of academic research and professional practice for many people within the library and information sciences (LIS). This article is an exploration of the concept of “meta­data.” It presents a high-level introduction to the topic with analysis of key research problems and practical challenges. The paper discusses varying understandings of what “meta­data” means, the origin and evolution of meta­data as an important topic within information and data fields, and the central characteristics of that which gets called “meta­data.” Meta­data can be understood as both process and product and can result from both human effort and computational techniques. Given the central role meta­data have in the establishment of know­ledge, evidence, and truth, it is necessary for researchers and professionals within LIS to think critically about our meta­data practices and systems.