VEGFR-2, also known as KDR or Flk-1, is a critical receptor tyrosine kinase that plays a pivotal role in angiogenesis and lymphangiogenesis by mediating the effects of VEGF-A. Its activation leads to a cascade of intracellular signaling pathways that promote endothelial cell proliferation, survival, migration, and vascular permeability, making it a key target in cancer therapy and vascular diseases.