CKEditor is a Wysiwyg editor (What You See Is What You Get) that integrates with Drupal. There are a number of Wysiwyg editors available, but I’m going to show you how to use CKEditor because it will be the editor that comes packaged with Drupal 8. So, using it now, will make the transition from Drupal 7 to Drupal 8 easier on your part.