Probiotic: microorganisms, present in food, that take up residence in the large intestine and contribute to the health of the intestinal tract.
Example: Yogurt contains microorganisms called lactobacilli. Eating yogurt we get lactobacilli.
Prebiotic: substances in food that increase the growth of probiotic microorganisms. Example: onions, bananas, and oranges contain fructooligosaccharides, which make the lactobacilli do well.
Note: a banana and yogurt is a perfect combination: it provides lactobacilli and food for the lactobacilli .