When you are editing a page, you are using a WYSIWYG (what-you-see-is-what-you-get) editor. JustEdit users have the latest toolbar and can edit pages without leaving the "Preview" view of the page.
Most users already have their editors set to JustEdit; if you're not sure, check your user settings. JustEdit will either be checked or not. If not, click JustEdit to switch over as JustEdit is recommended.
The toolbar is very similar to a word processor and most of the buttons are self-explanatory.
Here is detailed information on some specific functions within the toolbar:
For more information about the JustEdit, watch this video from Ou Campus: