Type O blood is one of the four main blood types, classified by the presence or absence of specific antigens on the surface of red blood cells. It is characterized by the absence of both A and B antigens, making it a universal donor type. This means that individuals with Type O blood can donate to any other blood type, which is crucial in emergency situations. People with Type O blood can receive blood only from other Type O donors. This blood type is also associated with certain health traits and dietary recommendations, as some studies suggest that individuals with Type O may have different nutritional needs compared to those with Type A, Type B, or Type AB blood.