It is the code that is used to show flash or video content.
Useful tutorial on its google blog:
Embed code is mainly used for embedding video onto web page. Not only video, but also audio uses embed code to play on web page.
To embed video to web page, www.playerdiy.com is a quick solution, check this tutorial about how to easily do this - http://www.playerdiy.com/supptarget="_blank"><img src="put link here" border="0"