This chapter will describe the biological nature of viruses belonging to the Coronaviridae family. Coronavirus disease or COVID-19 which, with its ever-expanding attack around the globe has become the topic of discussion of the current era. The disease is caused by a SARS-CoV-2 virus which belongs to the Coronaviridae family. This family of the virus has a history of pandemic significance through its attacks of SARS and MERS since the year 2000. They are known to have affinity towards respiratory tract and any disease that erupts out of their group have caused mild and severe respiratory infections globally. Thus, understanding the virus by learning the characteristics of its familial strain will help us to combat their attack even after mutation in the future. This chapter also discusses the pathogenesis of each virus organism in this family, as well as their clinical characteristics and diagnostics, in order to understand their disease-causing pattern and the efficacy of vaccination in mitigating the worst outcomes of the disease.