Prebiotics and probiotics are both good for your digestive health and therefore ideal for your health. Simply put, probiotics are living organisms like live yeasts and good bacteria that live in your body and are good for your digestive system. Prebiotics are needed to feed the probiotics. Prebiotics are not living, but rather a source of food for your gut's healthy bacteria. They are carbohydrates that your body can't digest, but they act like food to help the healthy bacteria grow.