Topic articles are encyclopedia-style articles which can be modified by any user who is logged in. These kind of articles have a specific focus on a certain subject, such as a biography, the history of a certain technology, or an IEEE section's history. There are thousands of topic articles on the GHN, so performing a search or browsing by category can be used in searching for content in addition to viewing a list of all topic articles.
Looking to edit topic articles? See the help section on writing topic articles.