Every federated wiki interprets a few plugin types the same way. Not only does this facilitate uniformity for basic formats, it allows the core code to use a few specialized formats without concern that the plugin might not be available. github
In our sloppy language we often refer to items of any type as paragraphs. Or we will refer to an item of a given type as a plugin of that type. We also refer to core types as plugins even though they are plugged at a very fundamental level. See JSON Schema
Basic Content
Simple text is of type 'paragraph' The markup includes single and double square brackets for hyperlinks. The text editor special cases return and backspace keystrokes to split and merge paragraphs. See About Paragraph Plugin
The 'image' item type provides uniform handling of images and their captions. The factory creates image items for dropped image files. Images are also used by many foreign format importers. See About Image Plugin
Specialized Content
The 'reference' item type creates a link to a specific page at a specific site. The site is added to the resolution context for links in the title and text of the reference. Search creates references. See About Reference Plugin
The 'future' item type stands for a page that has been cited but has not been found. The future provide various mechanisms, like templates and neighbors, to help create the desired page. See About Future Plugin
The 'factory' item type stands for an item that has been added but not yet specialized. The factory provides various mechanisms, like double-click, drag-and-drop, and the plugin-menu. Most commonly it becomes a paragraph, image or reference. See About Factory Plugin