Concept building: A bottom up hierarchy
Everything you know was learned in the context of prior knowledge. You combined prior experiences, refined them, and over time solidified them into new constructs which you then used to repeat the process for higher level concepts. Visual light and dark blobs become coherent shapes which get associated with meaning and eventually those meanings get associated with names like 'chair' or 'rabbit.'
Content access: A top down (and sideways) lookup.
In many cases we know what we want without bothering to think of the name. Being thirsty may mean you think 'glass','faucet','stream','bubbles', and 'water.' But you don't have to think any of those words to get a glass of water and take a drink.
Unfortunately in much of IT there is a textual interface so you first have to pick a starting word and then use that to find what you're looking for. Any time you think of a word it is physically connected to many other notions, memories, experiences, and other words built over a lifetime of experience.
When we try to describe what something is we access the hierarchy we have learned. A chair is a piece of furniture, which is a solid object, which is something I can touch. We may even use this description to create a hierarchical description.
The tension here is that how we describe things is at best a very limited subset of how our brain connects to information about that thing. These mappings differ from person to person and change over time. One system of hierarchical categorization cannot be intuitive to all people and probably won't be to the same person after 10 years.
IMNSHO The only interface which will 'just work' for organizing labeled objects is one that knows you. The best example of this is Google's one box which searches my computer, builds associations between content that are not directly related to the search terms I use, and modifies itself over time based on my behavior.