CKEditor is a text editor to be used inside web pages. It's a WYSIWYG editor, which means that the text being edited on it looks as similar as possible to the results users have when publishing it. It brings to the web common editing features found on desktop editing applications like Microsoft Word and OpenOffice.
Because CKEditor is licensed under flexible Open Source and commercial licenses, you'll be able to integrate and use it inside any kind of application. This is the ideal editor for developers, created to provide easy and powerful solutions to their users.
CKEditor is not a desktop application like Microsoft Word or OpenOffice. It's a component to be used by developers to enhance their applications. It's an editor to be used inside web pages.