Coronaviruses are the fascinating group of viruses with the unusual molecular mechanism of recombination and transcription and also consist newly emerged pathogens. The emergence of SARS and coronavirus as its etiological agent was found totally surprising in community of coronaviruses. As it was the first strain found to be causing severe illness in humans and also in moderate cases causes death. Till now there are found to be seven strains of coronaviruses affecting humans including newly found coronavirus. The NL63 strains and HKU1 strains both provide model for newly described identified human coronaviruses. Other strains OC43 MERS-CoV, 229E and SARS-CoV associated genome analysis showed identification and characterization of protease and replicase as well as various enzymatic activities of open reading frame ORF1a and 1b of these strains. All this provides us target for which potential drug can be evaluated. Various novel respiratory viruses including SARS-COV and NL63 were found in past 3 years. Then the discovery of another coronavirus HKU1 found in china. The other which had been recently emerged in Wuhan, China named as COVID-19. The genome of all strains of coronaviruses is described in this paper which will be helpful in decoding genome, diagnostics and prognosis of COVID-19.