Joomla uses an editor wherever content is created, in both the site administrator and the front end. Three are supplied with Joomla:

• TinyMCE — the default. A visual editor for articles, custom modules and any other rich-text field.
• CodeMirror — a source editor with syntax highlighting, used when editing raw HTML, CSS or PHP, such as when customising template files.
• None — a plain text box. Content has to be written as HTML by hand, which is awkward for articles but useful when markup must be preserved exactly.

The default editor for the whole site is set in Global Configuration, and individual users can override it on their own profile. Editor documentation