Tumor

A cluster of cells that have begun to divide uncontrollably.

Benign tumor -  is a growth whose cells do not spread to other organs in the body - however, if they continue to grow in the original area, their growth may cause pressure on adjacent organs.

Malignant tumor - is cancerous in nature, composed of cells capable of spreading. Without treatment, it may send metastases to additional areas in the body, to nearby tissues, and destroy them.  Sometimes, cells detach from the original (primary) tumor and spread to other organs in the body through the bloodstream or lymphatic system.
When these cells reach a new area, they may continue to divide and form new masses called 'secondary tumor' or 'metastasis'.

Tumor symptoms depend on its location. For example, a tumor in the lungs may cause coughing, shortness of breath, or chest pain. Tumors in the intestine may cause weight loss, diarrhea, constipation, anemia, and blood in the stool.