Cancer is a general name for a collection of diseases that are related and cause a division of cells in the body which eventually spreads to other parts of the body. It can begin from any part of the body, as long as there are cells there, and then it begins to grow and divide itself into multiple cells. When the cells grow old and die, new cells take their place and then the cycle goes on and on.
This continuous growth and break down of cells in areas where they are not needed may eventually lead to formation of a growth known as tumors. Tumors are masses of tissue which may spread to other nearby tissues or to other parts of the body to form fresh tumors. Some tumors are benign, which means they do not invade other tissues or grow back when removed, while some other tumors are malignant meaning they can spread to other tissues and grow back even when removed.