Varicose veins are swollen, twisted veins that often appear blue or dark purple. They usually develop in the legs and feet due to weakened valves and veins, which can cause blood to pool. This condition is common and can be caused by factors such as age, pregnancy, obesity, and prolonged standing or sitting. While varicose veins are often not serious, they can lead to discomfort, pain, or more severe issues like venous ulcers or blood clots. Treatment options include lifestyle changes, compression stockings, and medical procedures to improve blood flow and reduce symptoms.