There is a Japanese taste term called umami - sometimes described as savoryness here. Japanese, and Asians, generally, understand umami as a separate taste. We have 4 (sweet, sour, bitter, salty) they have 5. These are tastes, as vs. smells, and there is real proof in work done with receptors on human tongues that shows that umami is indeed a separate taste.
MSG is used to enhance umami - it is somewhat sweet - but has to do more with a quality of "fullness" of flavor. Those of us raised on it immediately understand - but anybody can develop an understanding of what the taste is. Of course, it can be a negative understanding - people who react negatively to the MSG taste sensation (other than reacting to the totally discredited mass hysteria of the 70's & 80's) could have a sensitivity to the taste, and react negatively, much as others do to bitterness or sourness.
Sometimes it's just a matter of strength - lots of us like slightly sour items, especially when it's mixed with sweet, but can't stand extreme sourness.