We all grew up knowing we had 4 senses of taste... sweet, salty, sour, and bitter. And, then there's umami - the sense of savory. Umami is when the sense of taste combines with the sense of smell - to bring about the enhancement of flavor.
A great example was given last night. Imagine you are completely blindfolded with your nose plugged, and someone puts a jelly bean in your mouth. You didn't see the jelly bean beforehand, but you are able to sense, through taste, that it's either: sweet, salty, sour, or bitter. But, you don't really have the ability to identify the flavor of the jelly bean until you unplug your nose and utilize the sense of smell. That is umami.
Chef explained that most of us have items in our home that have Umami, such as ketchup, soy sauce, parmesean cheese, red wine, etc. These things are added to foods to make them savory and robust.
He recommended the book The Fifth Taste: Cooking with Umami by David and Anna Kasabian.