CKEditor is an online WYSIWYG editor that produces clean, standards-compliant HTML code. This means that you can write the text in the editing area and format it in a few simple clicks of the toolbar buttons without knowing the ins and outs of the HTML syntax.
This is how a sample text appears in the editing area:
If at any time you would like to check the HTML source code of your document, use the button from the toolbar. The text that will appear in the editing area contains all the relevant HTML tags and attributes.
Do remember though that HTML editing is an advanced feature and its use is limited to users with knowledge of the HTML markup language. CKEditor lets you format the text or insert media like images or links without worrying about the source code and tags.