They are WYSIWYG (What You See Is What You Get) editors, that could replace the default editor of xoops. They could provide more options when writing news, forum messages, articles and so on.

An article comparing them could be found here:

http://www.entornoambiental.com/uploads/WYSIWYG_EDITORS_REVIEW.pdf

How to use them depends on the version of xoops (2.0x or 2.2x - check for compatability between your version and the editor) and modules you whant to use them on. Some modules have an build in editor, or support for some of them. In other cases you need to change some files for the module - have a search in xoops support forums.