How to get headings and image dynamically appear in a web page (on scrolling)

Can some one explain the technologies/framework/plugin use to get following two effects in web pages. (1) get some headings and descriptions appear progressively (dynamic) while scrolling. (2) adding background image dynamically while scrolling.

Both the features are found in the following site.

http://www.juraa.com/

Is it Bootstrap with other technologies or completely different framework stack.

Thanks.