Polycythemia Vera is a chronic myeloproliferative disorder characterized by an overproduction of red blood cells from bone marrow due to a mutation in the JAK2 gene. This leads to thickening of the blood and complications like blood clots and spleen enlargement. It is diagnosed through blood tests showing increased red blood cells. While there is no cure, treatment focuses on reducing blood cell counts through regular blood removal and medications to suppress bone marrow production and stimulate the immune system.