Glossaries in the category Category:Glossaries are lists of terms with definitions, where each list is selected for a particular domain such as "golf" or "graph theory". They are located in the Appendix namespace. The definitions found in Wiktioanry glossaries are content whose master record is in the main namespace: the glossaries could in principle be created almost robotically from mainspace, if only topical categories were marked on the sense level. Compared to mainspace or a plain list of terms without definitions, a glossary provides for each term that definition among several ones which fits to the domain of the glossary. Glossaries concentrate only on definitions to the exclusion of other lexicographical information such as etymologies and translations, making it easier for the reader to learn meanings for a group of terms that are interrelated, one term defined in terms of another one, which in its turn is defined in terms of yet another one. When online, the reader can peruse one page for a set of terms to learn their meaning instead of having to open many individual pages. The reader can print a glossary, and learn the definitions of the terms offline.
Formatting of Wiktionary glossaries varies. Many are formatted using definition list: the definitions are of the form "; ] : definition"; see Appendix:Glossary of legal terms. Others are formatted using boldface and bullet lists: the definitions are of the form "* ''']''' - definition"; see Appendix:Glossary of rhetoric.
Names of glossaries usually follow the model "Appendix:Glossary of <domain>" or "Appendix:Glossary of <domain> terms", the former being more common. Examples include Appendix:Glossary of golf and Appendix:Glossary of nautical terms. Naming patterns that I reject include "Appendix:<domain> terminology", above all because it does not indicate that the page is a glossary.