Immunotherapy treatments are having their moment in the spotlight thanks to high-profile success stories and an influx of new cash and innovations in research. Former President Jimmy Carter announced that he was cancer-free just seven months after telling the world that his advanced-stage melanoma had spread to his brain. His remission is, at least in part, the result of immunotherapy treatments. And tech billionaire Sean Parker recently pledged $250 million toward cancer research programs involving promising immunotherapy treatments.

But what exactly is immunotherapy and how does it work? We've broken it down for you with this primer.

What is immunotherapy?

It helps to start with a basic understanding on how the immune system works. When a foreign body — such as a germ or an allergen or a cancer cell — is detected in the body, the immune system responds by sending cells to attack and neutralize the intruder. At least that's how it's supposed to work. But some cancer cells are able to turn off those cancer-fighting cells, and this is what allows them to multiply unchecked. Unlike traditional medications that block or circumvent the immune system, immunotherapy stimulates a person's immune system to help it fight diseases.

Some immunotherapy treatments use what's called checkpoint inhibitors to block the mechanism that cancer cells use to fly below the radar, reports the American Cancer Society. This lets the immune system do its job of destroying those cells. Another type of immunotherapy called cell therapy involves removing the immune system cells from the patient and genetically altering them to seek out and destroy cancer cells before injecting them back into the patient. In still another type of treatment, cancer patients are injected with proteins that attach to both cancer cells and the immune system's disease-fighting T-cells. This forces the T-cells into the fight and spurs them to destroy the cancer cells.

What types of diseases are treated with immunotherapy?

Immunotherapy has been successful in helping to minimize the symptoms felt by allergy sufferers. According to the American College of Allergy, Asthma & Immunology, allergy shots — or subcutaneous immunotherapy — are the "only treatment that changes the immune system and prevents new allergies and asthma from developing."

There is also promising new research in using immunotherapy to treat Alzheimer's disease.

But by far, the biggest advances in immunotherapy research have come in the form of its potential use to treat cancers such as melanoma, Hodgkin's lymphoma, leukemia, lymphoma, and lung, kidney and bladder cancers.

Does it work?

With researchers constantly performing new studies, the statistics are evolving when it comes to immunotherapy effectiveness. According to this recent New York Times article, 20 to 40 percent of cancer patients have benefited from checkpoint inhibitors while 25 to 90 percent of blood cancer patients have seen improvements from cell therapy depending upon the type of cancer treated. Some of these patients have had remissions that lasted for years; others had relapses within a few months.

Some of the highest success rates have been in patients treated with both the old and the new types of treatment. Combinations of radiation and immunotherapy — such as the treatments Carter used to beat back melanoma — or chemotherapy and immunology have researchers excited about the possibility of a true cure.

What is the future of immunotherapy?

Earlier this year, President Barack Obama announced an initiative called Cancer MoonShot 2020, which is billed as a four-year race to subdue cancer by the start of the next decade with the "ultimate goal of vaccine-based immunotherapy tailored to the unique tumor signature of individual patients."

Immunotherapy is the cornerstone of the Cancer Moonshot research. Health experts hope that by using these tools to rethink cancer, we can better learn how to help our own bodies tackle the disease.