The document discusses the importance of defining and describing collections in libraries. It notes that while digitization efforts have increased access to some materials, only a small percentage of total holdings have been digitized. Creating collection descriptions can help provide context and improve discovery of both digitized and non-digitized materials. Collection descriptions are useful for several purposes, such as increasing visibility of special collections, creating curated topic-based corpora, and aiding in search relevance. They also help in managing collections over time and addressing gaps. The document raises questions about what collections libraries have and whether they have structured descriptions to share.