Probiotic supplements come in mostly in capsule form though there are others, and there are many brands to choose from. You can find them in health food stores or pharmacies and are a great way to keep your good bacteria topped up to prevent or fight candida infection in the intestinal tract, and to help with digestion. Some people take them regularly and some use them when on antibiotics or when they have an infection.
Choosing which probiotic supplement to take can be confusing because of the different good bacteria there are, and because there are so many to decide between. Make sure you choose a well known and trusted brand, if in pill form make sure they are enteric coated so that the case or protective layer does not dissolve in the stomach acids on the way through, and you loose most of the good bacteria before they even get to the digestive tract. Check also about storage and use by dates. Some have to be kept in a fridge, and even supplements have use by dates.