* Normal cells have a built-in mechanism that regulates their growth and division. They stop growing and dividing when they come into contact with other cells or when they receive signals that the body doesn't need more cells.

* Cancer cells have bypassed this control mechanism. They continue to grow and divide even when they shouldn't, leading to the formation of a tumor.

This is just one characteristic, and cancer cells can exhibit many others, such as:

* Invasiveness: Cancer cells can invade and destroy surrounding tissues.

* Metastasis: Cancer cells can spread to distant parts of the body.

* Angiogenesis: Cancer cells can stimulate the growth of new blood vessels to supply them with nutrients.

* Genetic instability: Cancer cells have a high rate of mutations, which can lead to more aggressive growth.

It's important to remember that cancer is a complex disease with many different types, each with its own unique characteristics.