Drupal's taxonomy system is one of its most powerful features and also one of the more tough things to wrap your head around.  Taxonomy can be used to categorize content -- tags that identify what the content is about -- and this can extend to showing only content that fits that category.  For example, you could identify books by subject matter and then on different landing pages only show that kind of book.  Taxonomy leverages the power of labeling and that power can then be let loose using merlinochaos' excellent Views module.