Probiotics is people being given live beneficial bacteria because the general public is ignorant and scared of bacteria even though most are perfectly harmless and many more are good than bad. The term is a PR campaign. Yes you have all kinds of normal flora in your gut, on your skin, in your mouth and such. There is one bug that is supposed to be in the gut that if it is not there one would be at a much higher risk of developing kidney stones and if it were reintroduced then the risk would go away (a prof at Iowa State discovered this). Just because you have normal flora it does not mean that probiotics would not help, as that study proved they can be very beneficial, it is like taking vitamin supplements!
~~Nonpathogenic microbes are our friends~~