The "article" is the right-hand pane (or "article pane") which contains the actual text editor. Each node inside the tree pane corresponds to a text-document inside the article pane.
Since TreePad's article pane contains a text editor, you can type in a text, edit your text, delete characters, select blocks of text with your mouse or the keyboard, use the "Edit" menu, "Insert" menu, "Format" menu or "Article popup" menu.
With the "Edit" menu you can cut, copy, paste, delete, undo or "select all". The "Insert" menu contains functions to insert a date, time, date+time, text-hyperlink to a file or the actual contents of an entire text file. The "Format" menu also has some useful functions for changing the selected text to upper- and lower-case, removing leading spaces, removing return characters.
The article popup menu - you can activate it by right-clicking on the article - contains all of these functions, as well as "Article search", "Find next", and article "Navigate".
When you have finshed editing an article text, you can select another node. After this, the text-document that you have edited is automatically stored inside the original node. Moreover, the text-document of the selected node will become visible inside the article pane.