If you ever seen or used "phpkb" you will know what im talking.
A button in the wyswyg give you a list to insert and also preview before insert of elements that come as default or also you can create your own. Things like tips text block, alert text block, and many other. Also let you create your own block. For example if you use an alert message on some articles like "This article apply only to shared hosting" and you wish with bootstrap alert format, you simply create it and you have it as a predefined element. So then when you create an article and need it, simply select it from the list in the wyswyg and insert it. There are a lot of elements needed as predefined, like tips, alert messages, notes, notices. (all bootstrap styled).