Probiotics contain different types of microorganisms such as yeast (saccharomyces boulardii) and bacteria (such as lactobacillus, bifidobacterium). Microorganisms are found naturally in the stomach/intestines/vagina. Certain conditions (such as antibiotic use, travel) can change the normal balance of bacteria/yeast. Florastor is used to improve digestion and restore normal microflora.