Immunity is the body's ability to resist or fight off infections and diseases. It involves a complex system of cells, tissues, and organs that work together to identify and eliminate harmful pathogens, such as bacteria and viruses. This defense mechanism is crucial for maintaining health and preventing illness. There are two main types of immunity: innate immunity and adaptive immunity. Innate immunity is the body's first line of defense, providing immediate but non-specific protection. In contrast, adaptive immunity develops over time and is specific to particular pathogens, often improving with repeated exposure, such as through vaccinations.