Yeah, this has been awhile since I've done some reading but this crap activates taste buds on the tongue. It's one of the "flavors" the tongue can register. Too much basically chokes out that taste bud 'receptor' and blammo, you're foaming at the mouth... not really, but you get my point.
Typically what I do with it regarding steaks and burgers and stuff is I simply add it together with some salt. I'll measure out the salt for the container, and then add about 1/2 a TB of MSG into it, and shake it up real good. Then I sprinkle that over steaks or fish or whatever, if I'm going that route. Same with burger seasoning, typically it's kosher salt, pepper, onion powder, and a liiiitle bit of garlic powder, then a little bit of MSG, and boom, burger seasoning.
It's a useful tool in the culinary toolbox, I don't use it on everything, I can't remember ever really throwing it onto any kind of pasta or pasta sauce for instance, like ever.. or in my breads, or baked goods, but it goes great things for the homemade other stuff I mentioned, and it does great things with veggies.
The Life of the Knife is Ended By! The Wife.