Open source software (OSS) is a type of software with publicly available source code that can be freely used, modified, and redistributed, offering significant benefits to developers and businesses alike. Originating from a backlash against proprietary software in the late 1970s and 1980s, OSS promotes collaboration and innovation within the software community. Various open source licenses, such as GPL, MIT, and Apache, define the terms under which software can be used and shared, with distinctions between copyleft, non-copyleft, and quasi-copyleft licenses. These licenses ensure software can be redistributed, modified, and used commercially, while prohibiting discrimination and maintaining consistent licensing terms. OSS offers advantages including reduced development costs, increased reliability, and community-driven improvements, making it a popular choice for developers and companies. However, users must understand the specific licenses and potential legal implications to utilize OSS effectively and legally.