Looking for a plugin

… that enables me to add an image or advertisement within a text that appears when you scroll. Several news sites have this feature but I can’t find how it is called and thus can’t find any plugin that might accomplish this.

This Theme has an extension for exactly this use case. It is called Content Dock.

He is the link with a description.

That’s not what I mean, the Content Dock exists outside the pages content. What I mean is a plug-in that lets you put an advertisement or image inside the text itself that appears when you scroll at a certain percentage: where the text is there literally appears an advertisement or image, some even have some sort of parallax option with it. Can’t find an example right now (how typical if you need one) but I encounter it regularly. Not sure if want to use it but I’d like to know how in case I might.