From Porniki

Breaking the glass 

In movies or video, this is basically addressing the audience directly, admitting that in fact there is a camera and they know that they are being filmed.

This method is used often in television shows, such as Malcolm in the Middle, to allow individual characters to express something that might not otherwise be said. In some instances, all other action freezes while this character breaks the scene to talk directly to the audience, and then picks up where they left off.

In porn, this is a common occurance, as the presence of a camera (and cameraman) is often acknoledged, and often the cameraman is also interviewing or offering encouragement during the video shoot. The glass is never really broken, because there was none there to start with. This is a technique seemingly started by Ed Powers.