What is the difference between a lymph node and sub mandibular gland?

Let me explain: Salivary glands located beneath the floor of the mouth. In humans, they account for 70% of the salivary volume and weigh about of 15 grams. A lymph node is an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach and linked by lymphatic vessels.

Different functions: Glands secrete fluids like saliva or hormones (salivary, pituitary, etc.). Lymph nodes "taste" the lymph for anything bad like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well. They do not secrete anything.