A WYSIWYG html Editor is a tool for creating web pages on the fly.
It's does exactly what it says -
What You See Is What You Get
You just write the text and the WSYSIWYG Editor adds the html code behind the scenes.
It is turned off by default on new sites.
To Enable the WYSIWYG Editor
1. Under 'Master Settings' choose 'Custom Settings'
2. The very first field is 'WYSIWYG'
3. Choose 'Tiny MCE 4' from the drop down menu
4. Press the 'Apply Changes' button at the bottom of the page