Last year was the fisrt time I heard that word. My neighbor was taking them and was raving about how much better her overall health was. She is in her 50's and works out eats little, mostely veggies.
This is a FYI on them....
Probiotics are live microorganisms thought to be healthy for the host organism. According to the currently adopted definition by FAO/WHO, probiotics are: "Live microorganisms which when administered in adequate amounts confer a health benefit on the host".[1] Lactic acid bacteria (LAB) and bifidobacteria are the most common types of microbes used as probiotics; but certain yeasts and bacilli may also be helpful. Probiotics are commonly consumed as part of fermented foods with specially added active live cultures; such as in yogurt, soy yogurt, or as dietary supplements.
Experiments into the benefits of probiotic therapies suggest a range of potentially beneficial medicinal uses for probiotics. For many of the potential benefits, research is limited and only preliminary results are available. It should be noted that the effects described are not general effects of probiotics. Recent research on the molecular biology and genomics of Lactobacillus has focused on the interaction with the immune system, anti-cancer potential, and potential as a biotherapeutic agent in cases of antibiotic-associated diarrhoea, travellers' diarrhoea, pediatric diarrhoea, inflammatory bowel disease and irritable bowel syndrome.[15]

All effects can only be attributed to the individual strain(s) tested. Testing of a supplement does not indicate benefit from any other strain of the same species, and testing does not indicate benefit from the whole group of LAB (or other probiotics)
Etymologically, the term appears to be a composite of the Latin preposition pro ("for") and the Greek adjective βιωτικός (biotic), the latter deriving from the noun βίος (bios, "life").[2]
At the start of the 20th century, probiotics were thought to beneficially affect the host by improving its intestinal microbial balance, thus inhibiting pathogens and toxin producing bacteria [3]. Today, specific health effects are being investigated and documented including alleviation of chronic intestinal inflammatory diseases,[4] prevention and treatment of pathogen-induced diarrhea,[5] urogenital infections,[6] and atopic diseases.
History does tell us about the ways different cultures promoted their intestinal health before modern times. In the past, people used fermented foods like yogurt and sauerkraut -- as food preservatives and as support for intestinal and overall health.
Fermented foods are part of nearly every traditional culture. As far back as Roman times, people ate sauerkraut because of its taste and benefits to overall health. In ancient Indian society, it became commonplace (and still is) to enjoy a before-dinner yogurt drink called a lassi. At the end of the meal, they'd have a small serving of curd.
These Indian traditions were based on the principle of using sour milk as a probiotic delivery system to the body.
Other examples are all around us. Bulgarians are known both for their longevity and their high consumption of fermented milk and kefir. In Asian cultures, pickled fermentations of cabbage, turnips, eggplant, cucumbers, onions, squash and carrots still exist today.
You see, the processed foods that are so convenient also tend to upset the balance of bacteria needed to support overall intestinal health. What's more, many food products today are pasteurized or sterilized during the production process, and this destroys the helpful bacteria needed to promote intestinal health.
https://probiotics.mercola.com/probiotics.html
https://en.wikipedia.org/wiki/Probiotic