Cancer is so awful, but I really don't know how it works or why its so hard to cure.
Cancer is kind of an umbrella term for a group of diseases that involve abnormal cell growth. The cells go out of control and invade the other parts of the body. 
Ohh so is it just hard to near impossible to stop the intrusive cell growth?
If you remove one tumor, there's the chance another one will grow somewhere else. Benign tumors, in contrast, don't spread. They're easily removed and treated. 
Damn that's insane. So how does chemo work? Does the radiation slow or stop the growth of these cells?
Chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents) as part of a standardized chemotherapy regimen. Chemotherapy may be given with a curative intent (which almost always involves combinations of drugs), or it may aim to prolong life or to reduce symptoms (palliative chemotherapy). Chemotherapy is one of the major categories of the medical discipline specifically devoted to pharmacotherapy for cancer, which is called "medical oncology"
age and as lifestyle changes occur in the developing world. The financial costs of cancer were estimated at $1.16 trillion USD per year .
Definitions.
Cancers are a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. They form a subset of neoplasms. A neoplasm or tumor is a group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely.
All tumor cells show the six hallmarks