Please tell me the difference between a swollen lymph node and a tumor?

Lymph node: A tumor is a collection or mass of cells anywhere it doesn't belong. A lymph node is a mass of cells "belongs" where it is and acts to filter lymph fluid, normal fluid released from cells in its neighborhood. Sometimes a lymph node becomes a "tumor" when it either filters cancer cells from a neighboring tumor which grow in it, or its cells actually become a tumor. Tricky but hope it helps.