WP Editor Widget adds a rich text widget where the content is edited using the standard WordPress visual editor.
The plugin adds a widget called "WP Editor Widget".
In the widget you can add a title, edit the content through a link and choose to output the title or not.
When you click the "Edit content" link the WP Editor appears above the content, much like the Add media button. Click "Update and close" and then "Save" to save your content in the widget.
The widget as displayed in Twenty Twelve.
You can choose to display the title.
The widget as displayed in Twenty Twelve with title output turned on.