The content dock functionality allows you to introduce new content to your users as they scroll down a page. It’s especially handy for calls to action i.e. when you want your visitors to do something like purchase your product or contact you.
The Content Dock can be added to any page, and it can be set to display based on how far your users scroll down the page. This one is set to 30%; when you get about a third of the way down the page, the content dock will appear.