MicroTiny is a so called WYSIWYG editor for editing pages. WYSIWYG stands for What You See Is What You Get. It works similar to a word processor, where you can select the style for the content and see how it is going to look on the page.
Among available WYSIWYG editors CMS Made Simple has decided to use MicroTiny (the stripped down version of TinyMCE). TinyMCE is among the most developed WYSIWYG editors, with regular updates, a large following and customizable features.
There are also other WYSIWYG editor modules available for download.