A "rich text" or "WYSIWYG" (What You See is What You Get) text editor gives your content editors a way to create and maintain content using an interface that looks and feels a lot like using a word processor. Formatting is applied using button controls, so the content editor doesn't have to know anything about HTML and can immediately see what the content is going to look like after it has been saved.
Drupal 9 / 10
Drupal 9 comes with the CKEditor version 4 text editor built-in, though it is a minimal version, so site administrators may wish to install additional features through CKEditor plugins.
NOTE: CKEditor version 5 is coming to Drupal 10, and is a complete rewriting of the CKEditor system. Because of this, we do not recommend anyone customize CKEditor 4 any further, as any customization will have to be redeveloped when upgrading to Drupal 10.
Drupal 7 does not come with any kind of rich text editor. There are two popular add-on options commonly used on campus: