This article comprehensively examines the history, diagnosis, genetics, diversity, and treatment of SARS-CoV-2. It details the emergence of coronaviruses over the past 50 years, including the coronavirus from 2019 and its subsequent mutations, along with updated information about this virus. This review explains the development and nomenclature of coronaviruses, their cellular invasion through glycoprotein spikes binding to ACE-2 receptors, and the mechanism of cell entry via endocytosis. Diagnosis methods for COVID-19, including nucleic acid amplification, serology, and imaging techniques like chest X-ray and CT scan tests, are discussed. Treatment approaches for COVID-19 are outlined, emphasizing healthcare, antiviral medications like Remdesivir, immunotherapy using convalescent plasma, and adjuvant therapies such as anticoagulants and vitamins. Moreover, this review includes mutated coronaviruses, such as the Delta variant and the Omicron variant, and their influence on vaccine efficacy. This review covers the characteristics and impact of variants such as B.1.1.7, B. 1.35.1, P.1, Delta, Delta plus, and Omicron, addressing their mutations that affect virus transmission and vaccine efficacy, with a brief overview of four WHO-approved vaccines and their effectiveness against potential new variants.