Novel coronavirus was first reported on December 2019 in Wuhan, Hubei Province, China and so far more than 33,00,000 infections and over 2,34,000 deaths have been reported. The detail mechanism of action of this virus to host cell or body is remaining unknown. This virus could transfer during human-to-human close contacts, with a basic reproductive number about 2.5. To identify the target for vaccine therapy or other antiviral drug design, it is important to understand the virus attachment mechanism to the host, replication, transmission, etc. This study is an overview of these mechanisms reported so far from different research groups. This review will help us to understand COVID-19 and its mechanism of action in human body.