Frostbite is a condition that occurs when tissues, usually in extremities such as fingers and toes, are exposed to extreme cold for an extended period. The exposure causes the blood vessels to constrict, reducing blood flow to the affected areas. This can cause damage or death of skin cells and underlying tissue due to lack of oxygen and nutrients. Symptoms include numbness, loss of sensation, white or blue skin discoloration, and in severe cases, blistering or gangrene. Frostbite is a serious condition that requires medical attention and can lead to long-term complications if not treated properly.