Probiotic refers to live microorganisms, primarily beneficial bacteria, that, when consumed in adequate amounts, provide health benefits to the host—typically by supporting gut health and improving digestion. In dairy products like yogurt and fermented milk, common probiotic strains include Lactobacillus acidophilus, Bifidobacterium, and Streptococcus thermophilus. These cultures help balance the intestinal microbiota and may contribute to immune system support.