MSG is short for monosodium glutamate.
MSG is a common ingredient added to many foods to enhance the flavor. MSG has a specific taste known as umami — the fifth basic taste alongside sweet, sour, salty, and bitter. Umami has a meaty flavor that refers to the presence of proteins in food.
The flavor-enhancing effects of MSG are due to its umami taste, which induces salivary secretion. In other words, umami flavors make your mouth water, which can improve the taste of food.
FDA considers the addition of MSG to foods to be “generally recognized as safe” (GRAS). Although many people identify themselves as sensitive to MSG, in studies with such individuals given MSG or a placebo, scientists have not been able to consistently trigger reactions.
Please don't take our word for it. See the links from the Food and Drug Administration and the Mayo Clinic