This document provides an overview of free and open source software (FOSS). It discusses the history of software sharing and development, the rise of proprietary software, and the free software movement started by Richard Stallman. FOSS tools like Linux have seen widespread adoption and now dominate areas like web servers and supercomputing. The document examines motivations for using FOSS such as cost savings, security, and avoiding vendor lock-in. It also discusses the competitive advantages that FOSS provides for both individuals and institutions.