They may appear differently depending on your theme and plugins, however these are the two main types on Editors.
Clicking on the Visual tab when editing content shows the WYSIWYG (What You See Is What You Get) editor.
Changes that you make here, are approximately what you will see on the website when viewing the post or page.
Most people will be familiar with WYSIWYG editors, as they appear in a large number of email and document programs, such as Outlook and Word.
Your theme may change certain things, such as colour and size, unless you set it manually in this page.
Alternatively, you can use the WordPress Text/HTML Editor by clicking on the Text tab.
Find out more about creating pages or creating posts.
