Layers are both built, and they are tasted. In the culinary world, this is known as a “flavor profile.”
A steak dinner with mashed potatoes and carrots is different from a pot roast, even though they contain the same nominal ingredients.
Just as wines all taste the same to someone who just wants something alcoholic to drink, 5 star foods taste the same as McDonalds to someone just looking for a bite to eat.
When you prepare a dish, you don’t just throw all the ingredients all together, there is a process for each one (or groupings, you don’t always just do one at a time), that brings out its distinctive flavors. You can then add another ingredient with its seasonings to alter that flavor, but if you had just put it all in at once, it would be distinctively different. You may even cook different ingredients separately, and only combine them at the end for the final plating.
Sometimes that is because you are caramelizing, and different things caramelize at different speeds, and will caramelize differently based on the heat, the moisture, and how crowded the pan is. Sometimes, it is because an ingredient will absorb any seasonings, so you leave it out till later, to allow the seasonings to flavor other parts of the dish, or you put it in sooner, so that it gets the seasoning flavor and the rest of the dish doesn’t.
When you eat a dish, the layers that you would be talking about are the distinct different flavors that you experience. You shouldn’t taste them all at the same time as soon as you put your fork in your mouth, there should be some flavors that come out first, and others that take longer to develop. It does require a recipe to be followed correctly, rather than just throwing everything in all together, in order to properly achieve this effect.
And of course, the first layer is the aroma. Before your tongue touches it, your nose smells it, and the aroma can be distinct from the flavor as well.
But, just as fine wines are wasted on the vast majority of people who are not able to experience the deep flavors that have been fermented into it (I am largely one of those, never cared for wine, except for to cook with), most people will not catch the subtle nuances of a complicated flavor profile.
I see a flavor profile similarity to any other work of art, and I can even visualize it, both in what I am tasting, and what I am creating. This lets me appreciate the work that was done by the Chef in perfectly caramelizing the onions and shallots before adding the garlic, that the reducing wine was properly evaporated before they added the main ingredient, that the food was seared with a dry heat before it was finished with a moist heat method… stuff like that. The same thing that differentiates a work of art from random brush strokes, or a symphony from a cacophony of noise.