JCK Editor is a complete editor in Joomla administrative panel. With this component you can create and edit your materials to make them more convenient in terms of reading, to change the display styles to implement, and much more.
JCK Editor – internal editor for Joomla

The extension is completely free, and it means that you don’t have to pay for the download. Of course, there are paid features, such as the purchase of special plug-ins. For example, if you in the source code show the syntax highlighter, you will need to download and install via the editor (in admin panel) this is a plugin called codemirror.
Don’t forget to enable and activate the plugins – otherwise they will not work… you should Also gently apply various plug-ins, as they can interfere with the General editor.
When you install a component in Joomla you will apply the basic settings that you can change via admin panel.
Overall, I believe that the editor of Joomla could not be more suitable for different purposes, because it offers a huge number of special functions. The only caveat is the small glitches (such as the preservation of the article in the code view and save the material, and you have to switch the mode of the main editor window). Be careful to copy the contents of the material before it is stored in the system.
The ability to edit any material with HTML code or an external editor.
Fast download of scripts support for external style sheet.
Simple integration into the available settings and parameters.