Vitamin C, what is it? I could try to write something clever - but I think the Mayo Clinic has done a great job! Here it from them:
 
"Vitamin C (ascorbic acid) is a nutrient your body needs to form blood vessels, cartilage, muscle and collagen in bones. Vitamin C is also vital to your body's healing process. Vitamin C is an antioxidant that helps protect your cells against the effects of free radicals - molecules produced when your body breaks down food or is exposed to tobacco smoke and radiation from the sun, X-rays or other sources. Free radicals might play a role in heart disease, cancer and other diseases. Vitamin C also helps your body absorb and store iron.
 
Because your body doesn't produce vitamin C, you need to get it from your diet. Vitamin C is found in citrus fruits, berries, potatoes, tomatoes, peppers, cabbage, Brussels sprouts, broccoli and spinach. Vitamin C is also available as an oral supplement, typically in the form of capsules and chewable tablets."
 
And, if you hate taking a ton of pills, try out these in gummy-form! Delicious!