What kind of organism multiplies inside living cells?

Viruses are unique among living organisms in that they require a host cell to replicate. Unlike bacteria, fungi, and parasites, which can often grow and reproduce independently, viruses cannot carry out metabolic processes or reproduce on their own. They consist of genetic material (DNA or RNA) encased in a protein coat and must invade living cells to multiply. Once inside a host cell, a virus hijacks the cell's machinery to produce copies of itself, often resulting in cell damage or death. This dependency on host cells for replication is a defining characteristic of viruses, making them distinct from other types of organisms.