This article is not necessarily targeted to those who already know search, but I love the following quote:
Taxonomy is the secret power behind some of the world’s most elegant search experiences.
Excerpt of the quote in context:
Taxonomy is the secret power behind some of the world’s most elegant search experiences. Sometimes keyword searches of the text itself aren’t enough to really give users highly relevant results. For example, to provide visitors with a search of recipes, being able to associate a recipe with a taxonomic node, such as “gluten-free,” “vegetarian,” “spicy,” “Thai,” or “Asian” provides many more options for user experience designers to give the searching public. If only the text of the recipe itself had been searchable, users would not be able to understand suggested uses for a recipe or be able to find certain recipes for certain occasions or interests.