The current pandemic disease (COVID-19) is caused by a highly infectious coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-Co- -2). It belongs to the family of Coronaviridae, subfamily Orthocoronaa-virinae, order Nidovirales. Coronaviruses (CoVs) are enveloped and spherical shaped pathogens with crown-like protrusions formed by S protein on the surface. The CoVs contain singlestranded positive-sense RNA with genome of 27-32 kb that encodes both structural and non-structural proteins. The Coronavirus genome encodes for at least 6 ORFs, among which two third parts include ORF 1a/1b, which encodes 16 non-structural proteins (nsp 1-16) that play a pivotal role in viral genome replication. The structural proteins are part of mature virion and include spike (S), envelope (E), membrane (M) and nucleocapsid (N) proteins. The S protein binds to the receptor (ACE2 or others) on the host cell and determines host tropism. Replication of CoVs is extremely complicated process and includes regulation at various stages including dependency on both the viral and host factors. The present chapter provides updated information about the morphology, genomic structure, properties and function of different proteins and their role in replication mechanism of SARS-CoV-2. The information about the proteins and their role in viral life cycle is likely to assist in the formulation of targeted therapeutic interventions and vaccines against this emerging respiratory pathogen.