Abstract: Lactic Acid Bacteria (LAB) are economically important organisms and existed in foods, soil, intestinal gut of animals, used as starter cultures for food fermentations such as yoghurt, cheese, pickles, sausages, fermented fish and fermented fruits. LAB are gram positive, catalase negative and non-spore forming rods or cocci. LAB include recently many genera such as Lactobacillus, Lactococcus, Leuconostoc, Carnobacterium, Streptococcus, Enterococcus, Vagococcus, Pediococcus, Allojococcus, Tetragenococcus and Weisella. A key for differentiation of LAB into genera is illustrated in this review and is based on easily determinable characteristics allowing a rapid assignment of a new isolate to any LAB genera. LAB produce organic acids, diacetyl, H2O2, ethanol, acetaldehyde, bacteriocins and antifungal substances. They are recently used as starter cultures for food fermentations with their use as probiotics, since, they were approved recently to tolerate acidic conditions of stomach, tolerate bile acids and bile salts of intestine and attach smooth human tissues. The medicinal uses of probiotics are discussed in the present review.