Carbon dioxide diffuses out of the tissues and into the blood, where it is dissolved in the plasma. While some of the carbon dioxide remains dissolved in the plasma, most carbon dioxide diffuses into our red blood cells.
A screencast is a digital movie in which the setting is partly or wholly a computer screen, and in which audio narration describes the on-screen action. It's not a new idea.
What's new is the emergence of a genre of documentary filmmaking that tells stories about software-based cultures like Wikipedia, del.icio.us, and content remixing. These uses of the medium, along with a new breed of lightweight software demonstrations, inspired the collaborative coining of a new term, screencast.