Umami is a Japanese word meaning good flavor. It is made from glutamate and ribonucleotide. It is found in some things such as meat, dairy and seaweed. Umami is subtle and blends with other tastes to expand on them and increase other flavors. Most of us would not even know it is present, we would just say this is delicious.
The other flavors that are considered primary are: sweet, bitter, sour and salty. It wasn't until recently that umami has started to claim the fifth spot. It was originally discovered as glutamate found in seaweed that the umami theory took hold.
From this finding the invention of Mono sodium Glutamate came to exist. MSG. MSG is umami. It enhances the sweet, bitter, sour and salty. Where do we get all these in the perfect combination? When we combine sugar, salt and fat. The combination is literally addictive. If the umami is added it becomes even more addictive. The combination becomes like brain candy. One of the foods most researched in terms of having all the qualities that humans enjoy. Doritos. You can't eat just one!
In terms of what can I do with this information, I would want you to take away this. Look at the food labels. Does it have sugar, salt, fat or MSG or anything that says glutamate? Realize that you will probably love it. Realize you will want more. Go in knowing. Just don't let it take you by surprise. You will be surprised at how much less you eat of it.
Example: Potato Chips. (pretty much any kind) Made with russet potatoes most likely. The carbs in a potato are sugar molecules. Fried in oil, which is fat. Seasoned with salt and sometimes some flavored powder, glutamate. Now you know.