This is a quote from WebMD.com –
“Probiotics are live bacteria and yeasts that are good for you, especially your digestive system. We usually think of these as germs that cause diseases. But your body is full of bacteria, both good and bad. Probiotics are often called “good” or “helpful” bacteria because they help keep your gut healthy.
You can find probiotics in supplements and some foods, like yogurt. Doctors often suggest them to help with digestive problems.”