Synonym for Section or Chapter.

All Posts are placed into one or several Categories. A Main category is always required. Additional categories are called Extra categories.

Categories can be organized into hierarchies of Sub Categories with an infinite nesting level.

Notes:

• Since it is impossible to place a Post into a Collection without going through a Category, all new collections are created with at least one default category, which may be called "Uncategorized". Without this category it would be impossible to place a Post into the collection.
• Even if you configure b2evolution not to display radio buttons for the main category, a main category will always be assigned internally.
• The main category is also always considered as an extra category internally. Therefore, selecting a main category through a radio button will also check the extra-category checkbox. Doing this allows for faster database requests when finding the posts that belong to a specific category or even a specific collection.