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. The immune system can be divided into two main types: innate immunity, which provides immediate defense, and adaptive immunity, which develops over time and offers long-lasting protection. Vaccines play a crucial role in enhancing immunity by training the immune system to recognize specific pathogens without causing illness. When a person is vaccinated, their body produces antibodies that can quickly respond to future infections. This process helps prevent diseases like influenza and measles, contributing to overall public health.