The software industry is growing very fast and often promises new development. It initially promises to change the market, but ultimately fails to remain as it is. Open source software (OSS) is software whose source code is published openly, usually available at no charge, and often developed by voluntary efforts. Open-source software is everywhere whether specifically in the form of applications nurtured by dedicated users or as a built-in digital platform used by millions of people. This type of software is developed, maintained and expanded both within and outside the private sector, through contributions from businesses, universities, government research institutes, non-profits, and people. The open source model presents a new paradigm for financing software in the interest of communities (e.g. health and education) also. It can be said that such projects are developing in some countries and the government is focusing on running pilot projects to test the feasibility of OSS approach for such software. OSS has also gained prominence in some specific segments of the software infrastructure market by beginning to take a significant share and a particular example of this is that Linux has been the fastest growing server operating system since 1998. In addition, open-source software (OSS) has attracted the attention of researchers as well as practitioners in recent years. Keeping this objective in mind, this paper has done a comparative study of the characteristics of OSS and CSS, reason of its use by researchers, and the study of the major and particularly useful OSS.