A host cell is a living cell that provides the necessary environment and resources for another organism, such as a virus or a parasite, to survive and replicate. These cells are crucial for the life cycle of many pathogens, as they supply the nutrients and machinery needed for reproduction. When a virus infects a host cell, it hijacks the cell's processes to produce more viral particles. This interaction can lead to various outcomes, including cell damage or death. Understanding host cells is essential in fields like virology and medicine, as it helps in developing treatments and vaccines against infections.