Pus is a thick fluid that can form in response to infection or injury. It is made up of dead white blood cells, bacteria, and tissue debris. The body produces pus as part of the immune response to help fight off infections and heal wounds. Pus is often seen in conditions like abscesses or boils, where it collects in a localized area. The color of pus can vary, typically appearing yellow, green, or white, depending on the type of infection and the body's response. While pus is a sign of infection, it is also a natural part of the healing process.