The open source software (OSS) development area of research presents a fresh and generous domain for analysis and study. In line with this, it is important to have a high-level understanding of the “open source phenomenon” before being able to delve deeper into specific niches of research. OSS presents a rich picture and because of that, both academics and practitioners have shown intense interest in producing high-quality literature. This chapter provides an initial understanding of what OSS is and how it has come to be the exciting research platform that it is today, attracting attention from various sources. In addition, we take an overview of the research streams that have formed in recent years, and the basic findings of attempts made to transfer lessons from OSS to other research areas.