The document discusses tagging and social bookmarking as ways to organize and retrieve information. It notes that tagging is simple, flexible, and tags can be aggregated. A taxonomy is a formal classification system, while a folksonomy allows for bottom-up collaborative tagging by multiple users. Folksonomies allow for evolving terminology and viewpoints but can be messy. To simplify, tags should use basic lowercase terms without punctuation. There are four types of tags: descriptive, resource, ownership/source, and self-reference.