Sitecore uses the Rich Text Editor as its default text editor. This tool allows you to modify any content contained within a rich text field. Within the Rich Text Editor, you can perform various actions, such as pasting text from Microsoft Word, finding and replacing text, inserting media items, creating or removing hyperlinks to internal or external pages, and adding symbols to your text.
There is a total of 4 Modes provided by Sitecore to customize the rich text editor tool panel.
Rich Text Default
Rich Text Full
Rich Text IDE
Rich Text Medium
In the template in which you want to change the rich text field configuration, provide the field source from one of the below sources:
<setting name="HtmlEditor.DefaultProfile" value="/sitecore/system/Settings/Html Editor Profiles/Rich Text Full" />
As explained above, you can change the Rich Text Editor configuration for a particular template as well as change the configuration globally.