What is the lymph system?

lymph node pathway: Lymph nodes are found throughout the body and are connected to each other by channels called lymphatics. Lymphocytes move back and forth in this system which also involves the blood, spleen and bone marrow in a large interconnecting network that protects the body from a large variety of invaders, and even cancer.

Fluid drainage: The simplified answer is that it is the drainage system for non-blood fluid, much the same way that veins are the drainage system for blood back to the heart. However, the lymphatic system also has important roles to play in the immune system, digestive/nutrient system, and other physiologic systems.