The probably easiest way to illustrate the concept of taxonomy and metadata is by using the “Hello, my name is…” introductory sticker you often see at conferences or class reunions.
There are different variations of the introductory sticker where they provide information about yourself regarding everything from names and professions, to where you live; in other words, an attribute of some sort. The same principle applies to media and digital assets. The media/digital asset management metadata is the collective term for all of the information an asset (or in the case of the introductory sticker: an individual) holds. One attribute (e.g. name) is a single piece of metadata. But in most likelihood, when working with digital assets, you will have access to a range of different pieces of information.
Now that we understand the role of metadata, we can continue the metaphor to explain media/digital asset management taxonomy. The taxonomy is simply the different information you have chosen to include on your introductory sticker, e.g. name, profession, city, etc. The more information, the better your ability to store them and perform much more detailed and advanced searches within the system.