Hepatitis B virus (HBV), belonging to the family Hepadnaviridae, is a double-stranded DNA virus. Its structure comprises an outer lipid envelope, surface antigen (HBsAg), core antigen (HBcAg), and DNA polymerase. HBV primarily replicates within liver cells, causing hepatitis. It participates in biological responses and signaling pathways through mechanisms such as integration of viral DNA into the host genome, promoting virus replication, and protein expression, thereby affecting cell function and immune response. HBV exhibits genetic diversity, divided into multiple genotypes and subtypes. These genetic variations lead to differences in viral transmission modes, disease progression, and treatment responses, particularly concerning antiviral therapy resistance.