A piece to camera is the television and film term used for when a presenter or a character speaks directly to the viewing audience through the camera.
It is most common when a news or television show presenter is reporting or explaining items to the viewing audience. Indeed, news programmes usually take the form of a combination of both interviews and pieces to camera.
The term also applies to the period when an actor, playing a fictional character in a film or on television, talks into the camera and hence directly to the audience. Depending on the genre of the show, this may or may not be considered as a breaking the fourth wall.