The HTML Editor Web Part is a wrapper of the ASPxHtmlEditor control. This Web Part provides the following site features after it is registered in the SharePoint environment:
SPxHtmlEditorWebPart
Allows the content it occupies in a Web Part Page to be edited using the ASPxHtmlEditor control.
Use ASPxHtmlEditor to edit Text fields
Substitutes a standard rich text editor (used to edit the content of columns whose type is multiple lines of text within SharePoint list pages) with the ASPxHtmlEditor control.