It's something we take for granted. The science of how we taste things is quite fascinating.
We may have 10,000 tastebuds from birth, but how you experience the taste of something (like great coffee! :) is a combination of using those tastebuds, your sense of smell and the texture or mouthfeel of your food or drink. It turns out the tongue map of old (dating back to 1901) with the regions for sour, sweet, bitter and salty could even be wrong - there may be a FIFTH TASTE called umami (for "brothy" or "meaty" tastes). The umami taste won't play a big part in tasting your coffee though.
We all taste things differently. Some of us could be supertasters (high concentrations of taste receptors) and more likely to take our coffee without adding anything like syrups or choc. And some of us love the sweet add-ons!
Our taste buds have about 10-50 cells responsible for tasting, and are replaced every 7 days or so. We do start losing taste buds from the age of 50 or 60 though, which may then lead you to seek out different flavours.
The Role of Smell
Much of the sensation of taste is due to our ability to smell, as we can discern thousands more smells than tastes.
So the tasting starts when we get that first whiff! stimulating nerves high up in our noses.
The Role of Texture
This is more about the psychology of taste, and how we interpret what we are eating or drinking. This is where texturing or "stretching" the milk comes into it's own, as it creates a wonderful sensation in the mouth. Or even for an espresso shot, savouring the crema (from fresh coffee) after pouring the shot is also important to your tasting experience.
Next time you take a sip of your favourite, take a moment and savour the flavour, the mouthfeel and the aroma. Then you're good to go ?