This document discusses free and open source software (FOSS). It begins with an introduction to FOSS, noting its freely available source code and focus on freedom rather than price. The history of FOSS is then outlined, including the founding of the Free Software Foundation and development of Linux. Key differences between free software and open source are defined. Advantages include access to source code and lower costs, while disadvantages include disclosure of trade secrets. Free software is said to better ensure certain freedoms for users compared to open source. Examples of FOSS projects and major websites are also listed.